an odd problem

My friend recently got Gmod and when he starts it up it comes to the loading screen but there is no blue loading bar it has the default Loading… in a black box in the corner like from CSS. Then it crashes…theres no error report or anything it just closes, ive tried rebuilding his cache but it still wont work, his comp can run CSS well and TF2 decently. has anyone else had a problem like this?
Please help if you can.