As I play the single player campaign, the game crashes after mission 3. I reach the portal and the mission accomplished message appears with the audio.

Pressing Exit map crashes the game and mission 4 stays locked.

Any idea, what might be causing this?

might be corrupted (quick)save? I've had it happen once or twice, but after restarting the level it went away...

Ok. Thanks. I started the mission again and used cheat to complete it (since I allready had completed it). Worked fine this time.

So, Thank yoy very much,