Chi, I vaguely remember something like your issues from AGES ago and ended up using a tiny app to reset a system component - I think it was something to do with DNS settings ???
Ahhhh...just had a mootch - it was an ipconfig command option and here is the site I found it from:
http://www.annoyances.org/exec/forum/winxp/1044982606 heres a good write up too:
http://www.ss64.com/nt/ipconfig.html good luck