You should have your firewall blocker on, be running both anti-virus AND anti spammer programs just to avoid anything like this. It does not have to come from any one website, but could be masking itself as somewhere you have been. There are probably a thousand programs installed on your registry that you don't even know is watching your every move. They mask themselves as being from websites you frequent so that you don't know to erase them or avoid them. Anyone who uses the interenet - especially a continuously running DSL line should be protected or you WILL, not might be suseptible to this. After this happening to me a few times, I now use Norton Antivirus with Auto updates, Spybot with autoblocker, and Adaware SE (not Adware - it is the bad one) ~~~ AND I still have to run the scans on all three at least once a week to keep myself protected. This site has nothing to do with it most likely. Just a thought to help you....
UPDATE: I just ran my antispam programs for the heck of it (ran them 2 days ago) and they found 20 changes to my registry and 7 spyware programs - good thing I checked! - If you don;t use these programs you probably have more than you would think possible...
All around fun person to be around :)