Have you run the repair tool? an you could try this don't know if it will work.
Albert Meyburgh, on 06 February 2014 - 02:40 PM, said:
vsync makes the shaders rebuild so it's probably related to a bug we've been tracking regarding the game getting corrupt during async shader compilation. we're possibly turning off async shader compile when dx11 is released but it's not my dept so I'm not sure. In the meanwhile if you delete your user shader cache, run the repair tool, and add r_ShadersAsyncCompiling=0 to your user.cfg it
MAY resolve the issue but no promises for now

Albert Meyburgh, on 07 February 2014 - 09:47 AM, said:
sorry I should clarify, if you follow these steps as I suggested, you can turn vsync off again, and since async compiling is disabled with that user.cfg flag, the corruption would thus be avoided in the future... so it is a permanent workaround in theory with no need to rely on vsync to force a rebuild... but no warranty as I said

I am just throwing it out there since I can appreciate the frustration.