I can tell you the answer, but you have to promise to let Cheeks out of the freezer first.
If it's the browser, and it's IE and FF causing the problem, then you can try another browser instead.
I'd also have a go at disabling any firewall/antivirus software too.
(Not just the tray icon, but stop the services if there are any)
If it's a problem with the IP stack, updated drivers will fix that.
If it's something wrong with the NIC then you can try another one if you have one kicking around.