SP2 popup blocker is the worst popup blocker in existance, heres an example.
I go on a website "Popup Blocked" and 2 seconds later a popup appears. Its like a one time thing, it will block 1 popup only, and then it wears off.
It wouldnt be plus, unless you have the sponsor (too bad is isnt something that isn't catagorised as malware
). Get ad-aware (www.lavasoftusa.com), if that doesnt work, scan for viruses, and then check for programs that might like to dwell as a toolbar: mywebsearch, Dashbar, coolwebsearch, etc etc.
Go through add-remove programs and look for anything with "search" in the name, and then post here anything suspicious.
Why did you block plus? i always say yes, because i know i didnt install the sponsor, and its safe.