HI,
Have you ran Spyware and also Virus scans? In SafeMode?
There is a good chance, whenever visiting or downloading from most "adult sites", that your computer might be infected.
The following site contains some very good information and steps, about getting rid of, or checking for, Spyware and Viruses:
Cleaning a Pest-Infested Computer
I am not sure if your computer has been infected, but if you haven't done the above, then it's really worth the effort to check it out. Best of luck.