Weird Google redirects?

When I try to visit certain sites, many porn sites in particular, it redirects me to Google with a seemingly unrelated search term.

Just what the fuck is going on? It didn't used to do this, and it doesn't do it on my other computer. I figured it was some spyware nonsense, but after running Spybot and AdAware for the nth time, the problem persists.

It's keeping me from my porn, and that irritates me.

Halp?

>>5

Start > Run
regedit
search > google

if u find something suspect, kill it with fire
else, disinstall-reinstall firefox and try again