Gmod Constantly Crashing

Hi iv been playing good for quit a while (1609hrs). This is probably my favorite game! But over the last two weeks I have not been able to play multiplayer servers. I join in the game, start to move around then I crash. I have completely erased my computer, and have been searching for a answer to the problem anywhere, but still nothing. Im at willing to do a lot to get this problem fixed.
Computer=Mac

Thanks,

Two theories:

  1. You need to turn down your graphics
  2. You have way too many addons.

All I can think of at the moment.