Go to your steamapps folder and delete all the .gcfs for any game related to GMod.
Quote from: RoflWaffle on January 09, 2013, 03:42:39 PMGo to your steamapps folder and delete all the .gcfs for any game related to GMod.Did that yesterday, along with deleting all of my source games and reinstalling only HL2 and Gmod. Same problem.I've heard that some other people have been having this problem and I'm really looking toward a fix so I can help out everyone that has the same problem.