I realised that if I del file ..\valve\steamApps\myUser\counter-strike source\bin\vidcfg.bin then I could play again. Then I made a file.bat whit the next instruccions:
del "C:\File Programs\Valve\Steam\SteamApps\myUser\counter-strike source\bin\vidcfg.bin";
"C:\File Programs\Valve\Steam\Steam.exe" -applaunch 240;
Change your display mode to a lower setting. (windows itself as well)
Try this as well. Looks as though it could also be bad vidoe cfg that needs to be cleared. (another poster referred to only having the problem after 3d polygon something was enabled.
Essentially the issue seems to appear when either the operation is too complex or too many operations are done at once.
The other thing with the decrease in colour settings is that it may limit what operations or functions can be called in DX9 etc.
Just a pity that no-one knows which operation/function is causing it.