Installation Problem

[toastybob42]

I have attempted to install Ubuntu 11.04 on an hp m7680n (http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&docname=c00739902&product=3230688) twice, once on both of the tower's 250 GB drives, in both attempts using a Live CD. Unfortunately, both attempts resulted in the installer program crashing partway through. After giving up and restarting without the Live CD, it seems that both actually resulted in bootable installations. However, I quickly found that I could not install anything, as both the Software Center and other methods seem unresponsive.
Opening Synaptic Package Manager results in this error:

E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.
E: _cache->open() failed, please report.

[darkod]

Did you use the same CD to install? Maybe you have a faulty burnt CD or corrupted image. Burn a new CD at low speed (8x or 10x) and also download a new image if you're not sure it's OK. Best to download from torrent.