Help with GarrysMod not opening

Hey guys i’ve been a loyal player since Gmod 9 and only recently my garrysmod will do the preparing to launch garrysmod thing, then the game will pop up for a second then close.

I’ve Re-installed garrysmod, CS:S and Hl2.
I’ve de-fragged all 3.
All my drivers are up to date
I’ve verified The integrity of all the games.
Oh and garrysmod is in windowed mode when it opens, if that helps.

Still nothing, does anyone have anything for me ?

Thanks guys,
Sarge

Fixed
-dxlevel 90 -fullscreen