I just got this same kick after not playing for a few months and then trying to log on, so apparently iv installed something in the past few months that pb doesn't like, though I haven't found the culprit yet.
from what iv seen some of the common programs that can cause this error other then viruses/Trojans are:
steam
xfire
anti-virus/anti-spyware programs
certain firewalls
certain driver updates or lack of updates
some programs for custom mouse/keyboard macros
ISO mounting software (eg. PowerISO, Daemon Tools...)
and probably a bunch of others...
So if you recently installed anything like that, try uninstalling/disabling it
I'm kinda screwed since iv done a lot of stuff in the past few months...hopefully your better off