whatfor

Hey guys, I need some help. Even steam's forums haven't answered anything yet.

So I can log on to steam fine, but the problem is where I can play in a Team Fortress 2 game for maybe a minute or two before getting the "Connection to VAC servers could not be made" or something like that. Same problem with Steam friends list, and Left 4 Dead has a "Stopping Search" error every time I attempt to find a versus/campaign game.

So I was wondering if anybody can give me any advice or solutions? I'll list what I can remember that I tried so far, even if they probably weren't what I was supposed to do. I got these from googling solutions and such.

-Reinstalling/Installing Steam
-Deleting the ClientRegistry.blob file and trying Warukuri's file
-Adding "-tcp" command to steam.exe
-Unplugging wireless router, and plugging it back in
-Deleting winui.gcf and a registry file named "Betas"
-Opting out of any betas