Everytime I try to start Portal2, it says 'Launching game...'. My friends get the message pop-up that I have started playing Portal 2. Then, after about 5-10 seconds I go back to being blue and out of game. Nothing else pops up, the game just simply won't start.
The kicker is that I was playing the game only a few weeks ago... What gives? And more importantly, why does no other game seem to have this problem??