Gmod Listening server crash on player join!?!?

Hello all ive been having problems with gmod latley and they have gotten worst over time. it all started people could join once but if they left and tryed to join again it would crash…then it progressed to if they didnt join in a timespan they would crash the server…now no matter what i try it crashes with an exception error or something like that to my desktop! please help!