Unusual Error(?) Message On Exit

All I did was exit Garry’s Mod, and this shows up.

http://img704.imageshack.us/img704/7656/boing.png

I have no idea what it’s referring to with all these "assert"s. I had to close the window though, because it wouldn’t let me switch windows. Anyone know what it’s talking about or why it showed up?

Probbably random or some memory faults

It kinda freaked me out. I’ve never seen something like that before. And what kind of file is a “.cpp”?