Perhaps there is a command that causes crashes that is usually locked due to sv_cheats but local and jump servers allow it to be turned on. I'm not an expert on this subject by any means but here's a way to troubleshoot if this is the case
Back up your cfg and try this: http://www.teamfortress.tv/30651/boost-fps-with-this-one-simple-trick
It should make most of your settings default or recommended. Then try to join a jump server
If I'm right then this should hopefully fix it. If it's fixed you can then use your cfg again.
If the crashes happens again then the cause is a command in your cfg which you can then hopefully find and remove