Hi all,
I was using UCK from 5 months now. Never I faced this issue.

Can anyone point out why this issue is coming?
Code:
Build (/usr/bin/uck-gui --wait-before-exit) started at 2011-09-27 09:04:06
>> Ubuntu Customization Kit 2.4.4 on Ubuntu 11.04, 2.6.38-11-generic i686
Starting CD remastering on  Tue Sep 27 09:04:06 IST 2011
Customization dir=/home/user/tmp/customization-scripts
Mounting ISO image...
Unpacking ISO image...
cp: reading `/home/user/tmp/remaster-iso-mount/boot/grub/loopback.cfg': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/casper/filesystem.squashfs': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/casper/initrd.lz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/casper/vmlinuz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/main/binary-i386/Packages.gz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/main/binary-i386/Release': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/Release': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/Release.gpg': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/restricted/binary-i386/Packages.gz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/restricted/binary-i386/Release': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/install/mt86plus': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/install/README.sbm': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/install/sbm.bin': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/b/b43-fwcutter/b43-fwcutter_013-2_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/b/build-essential/build-essential_11.5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/d/dkms/dkms_2.1.1.2-3ubuntu1_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/d/dpkg/dpkg-dev_1.15.8.4ubuntu3_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/d/dpkg/libdpkg-perl_1.15.8.4ubuntu3_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/f/fakeroot/fakeroot_1.14.4-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/g/gcc-4.4/g++-4.4_4.4.4-14ubuntu5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/g/gcc-4.4/libstdc++6-4.4-dev_4.4.4-14ubuntu5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/g/gcc-defaults/g++_4.4.4-1ubuntu2_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/l/linux-wlan-ng/linux-wlan-ng_0.2.9+dfsg-4_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/l/linux-wlan-ng/linux-wlan-ng-doc_0.2.9+dfsg-4_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/l/lupin/lupin-support_0.32_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/liba/libalgorithm-diff-perl/libalgorithm-diff-perl_1.19.02-1_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/liba/libalgorithm-merge-perl/libalgorithm-merge-perl_0.08-1_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/m/mouseemu/mouseemu_0.16-0ubuntu7_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/n/ndisgtk/ndisgtk_0.8.5-1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/n/ndiswrapper/ndiswrapper-common_1.56-3_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/n/ndiswrapper/ndiswrapper-utils-1.9_1.56-3_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/p/patch/patch_2.6-2ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/s/setserial/setserial_2.17-45.2ubuntu2_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/u/ubiquity/oem-config_2.4.8_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/u/ubiquity/oem-config-gtk_2.4.8_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvdial/wvdial_1.60.4_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvstreams/libuniconf4.6_4.6.1-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvstreams/libwvstreams4.6-base_4.6.1-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvstreams/libwvstreams4.6-extras_4.6.1-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/restricted/b/bcmwl/bcmwl-kernel-source_5.60.48.36+bdcom-0ubuntu5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/restricted/s/sl-modem/sl-modem-daemon_2.9.11~20100718-2_i386.deb': Input/output error
Unmounting /home/user/tmp/remaster-iso-mount...
Failed to unpack ISO from /home/user/tmp/remaster-iso-mount to /home/user/tmp/remaster-iso
Build ended at 2011-09-27 09:04:10
Build (/usr/bin/uck-gui --wait-before-exit) started at 2011-09-27 09:11:25
>> Ubuntu Customization Kit 2.4.4 on Ubuntu 11.04, 2.6.38-11-generic i686
Starting CD remastering on  Tue Sep 27 09:11:25 IST 2011
Customization dir=/home/user/tmp/customization-scripts
Removing ISO remastering dir...
Mounting ISO image...
Unpacking ISO image...
cp: reading `/home/user/tmp/remaster-iso-mount/boot/grub/loopback.cfg': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/casper/filesystem.squashfs': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/casper/initrd.lz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/casper/vmlinuz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/main/binary-i386/Packages.gz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/main/binary-i386/Release': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/Release': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/Release.gpg': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/restricted/binary-i386/Packages.gz': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/dists/maverick/restricted/binary-i386/Release': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/install/mt86plus': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/install/README.sbm': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/install/sbm.bin': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/b/b43-fwcutter/b43-fwcutter_013-2_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/b/build-essential/build-essential_11.5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/d/dkms/dkms_2.1.1.2-3ubuntu1_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/d/dpkg/dpkg-dev_1.15.8.4ubuntu3_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/d/dpkg/libdpkg-perl_1.15.8.4ubuntu3_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/f/fakeroot/fakeroot_1.14.4-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/g/gcc-4.4/g++-4.4_4.4.4-14ubuntu5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/g/gcc-4.4/libstdc++6-4.4-dev_4.4.4-14ubuntu5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/g/gcc-defaults/g++_4.4.4-1ubuntu2_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/l/linux-wlan-ng/linux-wlan-ng_0.2.9+dfsg-4_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/l/linux-wlan-ng/linux-wlan-ng-doc_0.2.9+dfsg-4_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/l/lupin/lupin-support_0.32_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/liba/libalgorithm-diff-perl/libalgorithm-diff-perl_1.19.02-1_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/liba/libalgorithm-merge-perl/libalgorithm-merge-perl_0.08-1_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/m/mouseemu/mouseemu_0.16-0ubuntu7_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/n/ndisgtk/ndisgtk_0.8.5-1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/n/ndiswrapper/ndiswrapper-common_1.56-3_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/n/ndiswrapper/ndiswrapper-utils-1.9_1.56-3_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/p/patch/patch_2.6-2ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/s/setserial/setserial_2.17-45.2ubuntu2_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/u/ubiquity/oem-config_2.4.8_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/u/ubiquity/oem-config-gtk_2.4.8_all.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvdial/wvdial_1.60.4_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvstreams/libuniconf4.6_4.6.1-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvstreams/libwvstreams4.6-base_4.6.1-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/main/w/wvstreams/libwvstreams4.6-extras_4.6.1-1ubuntu1_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/restricted/b/bcmwl/bcmwl-kernel-source_5.60.48.36+bdcom-0ubuntu5_i386.deb': Input/output error
cp: reading `/home/user/tmp/remaster-iso-mount/pool/restricted/s/sl-modem/sl-modem-daemon_2.9.11~20100718-2_i386.deb': Input/output error
Unmounting /home/user/tmp/remaster-iso-mount...
Failed to unpack ISO from /home/user/tmp/remaster-iso-mount to /home/user/tmp/remaster-iso
Build ended at 2011-09-27 09:11:34
Thanks in advance.