Garry's Mod prop problems?

Ok so i have TF2 and i have installed/played it and for some reason in Gmod all of the model, materials, and props are all errors for me… The only way for me to fix this is to play TF2 and then go and play Gmod, after that i can see all of the TF2 stuff. I have to do this every time i want to play Gmod and see TF2 stuff. Does anyone else have this problem?