I click on Google result and I'm redirected to some Facebook page, advertisement or questionable website, why?

[imbri_karma]

I asked a question earlier but I deleted because I felt it didn't give enough information.

I use Firefox 4 on Windows XP Home Edition SP3, completely up to date (yes,I've checked, twice).

For the past two days I have noticed that whenever I click on a Google result, a bookmark or any link I am redirected to some Facebook page containing some artists, or I am redirected to an advertisement or some other equally questionable website. I've noticed two of those websites are a page that asks me for some sort of verification, has a button and a text input box but absolutely nothing else, and some Facebook page.

There's a definitely five or more second delay when I load Google or when I click on a bookmark, link or Google result that was not present a few days ago, this is an entirely abnormal behavior.

I have scanned my computer multitudes of times, using both Advanced System Care and IObit Malware Fighter and have found nothing. I don't have anything strange programs or applications installed on my PC or on Firefox, I've checked and rechecked.

If it's something, it's something I can't see.

Any suggestions? I'm very much irritated.