For those of you stuck with an ATI card, cliffe has updated CS.net with word of a fix coming soon for the overflow issue involving ATI's OpenGL ICD:
Valve has informed me that they will have a small patch out for those running ATI cards having the "overflow" error messages. This will most likely occur tomorrow (Friday). Stay tuned right here to cs.net -- we'll have the patch as soon as it is ready.Sounds good, cliffe!