I've had this problem for some time, whenever I try to load the game it crashes as the powered by source screen fades out. I had the problem before, it fixed itself (somehow) and has now come back. I've tried uninstalling and reinstalling and verifying the game cache. Nothing seems to work.
As a side note, if I try to skip past the loading screens it just freezes anyway. The only way to close it when this happens is through task manager as it comes up as "not responding"