This is nothing new, McAfee has a tendency to false flag a LOT. We used to have all kinds of problems with them at my old company. You need to call them and get your site removed from the list. Better do it quickly because if it goes uncontested for too long they will share their lists with the others and then you have 10 antivirus companies to call instead of one. Most likely some ill-defined heuristic kicked in after the forum changed and caused the false alert. It's the same kind of BS with Firefox blocking "attack sites" or MS SmartScreen. It's good protection to have, but it's administered loosely and causes a lot of false positives. Even worse in some situations attackers will report a legitimate website, and setup a spoof that isn't blacklisted...