Game crashes when loading multiplayer.

Singleplayer loads fine. No problems at all. One day, game loads fine, everything is good. No changes in anything related to the game or source games etc. Then one day my friends and I decide we want to play, so I got and start loading up the server. I get to Loading resources, it gets a few bars into that, and then just crashes. It freezes up for a few minutes, not doing anything, then it CTDs. I’ve tried verifying game cache, reinstalling the entire game, reinstalling source SDK, and content the game is dependent on (Hl2, Tf2, Portal, etc.)
Nothing. Game still does it. The game didn’t update or anything when it started doing this, absolutely nothing has changed.

Additional tidbit of information I just found out-
I tried to do the same thing with Garry’s Mod 13 Beta, does the same exact thing. Hangs up in the same place, the whole lot.

Specs if you need em

Intel i5-2500 @ 3.3ghz
Nvidia GeForce 560 Ti 1Gb
8GB DDR3 RAM
1TB SATA Hard Drive