I won't say I have never received a pop up with PPT, as it has happened in the past. That was a quite a while ago though. Though as far as receiving a virus goes, I have not. Have you considered that perhaps if you did pick up a trojan it could have come for several other applications you might have been runing at the same time you visited the site?
Perhaps there was something else, some other website with pop ups that caused this. I have yet to receive a pop up from the PPT frontpage or PPT forums. I use both IE and Mozzila, Mozzila which comes with a pop up blocker and IE which doesn't. With neither of those web browsers have I received pop ups or anything else
, specially not since the new adverts have started.
What I advice is to try and do what you can to guard yourself, trojans are everywhere, in e-mails, programs, anywhere. Make sure you update your virus protection programs and run your spyware mgmt programs to detect anything you might have picked up. As this is the only incident I've seen in regards to this I asume it's probably something else causing the problem.