GMod crashes when trying to play certain gamemodes.

[MrDestroyer]

Usually, GMod works fine for me. But, when I attempt to play some gamemodes (PERP, Flood, Awesome-Strike: Source, etc) it crashes.
(I'm using a Mac, by the way)

Problem details if it's any use:
[URL]http://pastebin.com/QD6khLpQ[/URL]