Firefox Google Problem

[Michael1406]

In Firefox, when I google the words forum or forums, I get a page saying

  Quote

Google

Error

We're sorry...

... but we can't process your request right now. A computer virus or spyware application is sending us automated requests, and it appears that your computer or network has been infected.

We'll restore your access as quickly as possible, so try again soon. In the meantime, you might want to run a virus checker or spyware remover to make sure that your computer is free of viruses and other spurious software.

We apologize for the inconvenience, and hope we'll see you again on Google.

The page title oddly is 403 Forbidden. The Google bit at the top is text coloured like the google logo. The phrases virus checker and spyware remover link to different download.com pages. The phrases that trigger this change slightly, which makes me think a proxy with the same IP as me is spamming google or something. I can immediately use other phrases after, too.

I response I ran Spybot, which detected and fixed something in the Windows Security Center registry (something about VirusScanOverride-dword:0) and AVG free is running now. I've checked my startup processes, current running programs etc with WinPatrol free and I'll probably run ewido free soon too, and maybe Trend Micro's online scanner.

Any of you lot heard of this happening before, or is it IP/Google related?

Update before post: AVG found an infected zip + exe in my downloaded files folder in my documents, but the zip/exe was fine before now. Maybe some other program changed it? AVG classes it as Trojan horse Downloader.Generic.GUK