TF2 crashing. need help.

Every time im on a server, I can play for about 10 or so minutes before the game freezes. I cant do anything when that happens, and the only way I can get it to close is from closing it on task manager. But if I do that, then it still says my game is running even though I closed it. It wont let me play tf2 or any of my steam games, and I have to reboot my computer to fix it. I've tried re-installing the game, but it didn't fix it. I checked here and it doesnt look like anyone else is having this problem. But if you know why, please help!