Spam Bots resolved.
Just Got this message from Admins:
Hey guys. I did some checking and over the last 24 hrs, almost 2k bot accounts were registered for the site. Something was wrong with the human verification which we have now fixed. Also in good news, the anti-spam measures on the site blocked and deleted all but a handful of these accounts, one of which was the perpetrator of this flood of PM spam.
All remaining spam bot accounts have been banned. If anymore PM spam comes through or you get reports, let us know.