Condition Zero game keeps closing!!!

[British_Command]

Im playing on Counter Strike : Condition Zero and i am able to have the game up for like 20 mins and i can join servers, but after a while i join a server and half way through it closes the window, with no error window.

I dont know why this is happening any help???

Could it be an virus running an anonymous program in the background procceses?

Any help would be appreciated,
MrP