Source games not loading

[MiccyNarc]

As the title says. The Preparing to Launch screen pops up and then disappears. the little "working" animation on the mouse cursor appears, then goes away. Then nothing.
I have no idea what to do. I've verified the game cache several times to no avail.
I don't want to delete and redownload them because I have a bandwidth cap at my school. It can be bypassed but it's a pain in the ass.

Any suggestions?