It's doubtful you did any permanent damage to your card when overclocking, if you got no artifacts or problems while you were overclocked.
It may, however, be a lingering heat issue. Try opening your case up and putting a desk fan next to it, blowing air on your graphics card (or inside your case, in general).
I thought we told you that you should not be using CS:S beta for testing overclocks. Test some other game like Far Cry or Doom 3 and see if the same thing happens.
I'm not testing overclocks. I'm just saying look how ****ed up my game is. The same thign does not happen in other games, but I wasn't sure if CS:S uses something different than those games.
1) Uninstall your graphics card drivers and reboot.
2) Download and run driver cleaner. Then reboot.
3) Download and install the latest cataylst drivers available from ati's website.
See if your problem still occurs.
PS - As much as CS:S Beta seems awesome, it is still in Beta. Which means you shouldn't be worried if no other game is having graphical problems.
It's either:
a) Drivers
b) card is shorted
c) card is bad
Could be other things but those are the most likely.
When I installed a cold cathod light, the inverter was touching my case and shorting my card. Many of my textures in CS and other games were purple or a rainbow of wavy colors. I removed the inverter and it went back to normal.