Sorry, I figure here might be better then Steam Forums.

My TF2 doesn't work. I do not know why it does not work, but it freezes on start up, or it attempts to validate the cache, gets to 100% and hangs. Never validates, never allows me to run the game. I've attempted defragging it, reinstalling steam, reinstalling TF2, reinstalling TF2 and Steam...

I'm at a loss - and I quite enjoy TF2, so I'd really be very happy if I could play it anytime I wanted.

[Small side note. It will play fine after a TF2 update.]