[CLIENT] crashes 3 seconds after the game loads.

Whenever I try to play a match, the game crashes. Its about 3 seconds after the map loads, every time, every map.
It seemed to start in 5.4, but only crashing occasionally then and giving me the bug splat option. As it made games frustrating, I hadn't played for a while.
I saw 5.5 patch was released, and hoped this would fix my problem. Instead, its worse. I've tried repairing the installation, and re-installing it, no change. Any help or advice?