Here's how I removed the module thermal from my initramfs:
Remove the line "thermal" from the file (if this file is blank, something wrong happened, post here), then hit CTRL+X, Y, to save the file.
sudo su -
zcat initrd.img-2.6.24-19-generic > /tmp/directory.cpio/initrd.cpio
cpio -idv < initrd.cpio
Now you can find the boot line for your kernel and remove the acpi=off option. I'd also suggest removing quiet and splash if they're still there, that way you can see what's happening. Mine looks like:
find . -print0 | cpio -o0 -H newc -v > /tmp/initrd.img.cpio
gzip -9c /tmp/initrd.img.cpio >/tmp/initrd.img-2.6.24-19-generic
mv /boot/initrd.img-2.6.24-19-generic /boot/initrd.img-2.6.24-19-generic.bak
mv /tmp/initrd.img-2.6.24-19-generic /boot/
Your UUID won't be the same as mine, don't change anything in this line except for the bolded text.
kernel /vmlinuz-2.6.24-19-generic root=UUID=ba05d9a0-8436-400d-9a6f-f0d041fb94e3 ro noapic
Best of luck. Post with any progress.