Reliable Snapshot Overflow

When I try to record anything in garrysmod with source recorder I get disconnected and this shows up:

http://img839.imageshack.us/img839/36/sssjf.jpg

This only happens in gm_bigcity, any ideas on how to fix this?

Is this Multiplayer or Singleplayer?

Singleplayer.

System Specs?

Memory: 2048 MB RAM
Processor: Intel Dual-Core 2.50Ghz
Video: GeForce 8600 GT
And running on windows 7.