The Ubuntu Software Centre has become broken on my home machine, (partial download, back to 50%, then error: port 8080 invalid host name). Since no one seems to be able to fix it, is it possible to:

1. Re-install that part of the OS without trashing the whole installation?
2. Since browsing, e-mail and FTP all work just fine, is it possible to get an install file and (then) install from a HD or USB or CD?

If the USC must remain permanently dead on that machine, I won't mind if I can get the programmes by some other method. Help, s'il vous plait!