The firewall might be at fault or a security program of some sort corrupting the file because it's being checked whilst downloading. Just a guess.

When upgrading versions of LW, you sometimes need to remove your previous allowance for LW in the firewall, then re-add it. See Setting up an exception for LimeWire in your software firewall (click in link). If Windows XP firewall is on, disable it. Only one firewall is needed. Find Windows firewall via control panel.

Also double-check your comodo security settings.

Another thought is defragment your drives. No other program should be running at this time however.