I'm not certain that the issue is exclusive to the video card, but here goes.
This system is about four months old and never had an issue. Very recently I've been experiencing some erratic performance glitches. Games will run fine, but every so often, maybe every ten seconds, it freezes for a split second. It's very quick but enough to break the immersion.
Also just now I happened across a second weird issue. I was watching a movie in CyberLink PowerDVD 11 when I started resizing the window vertically, at which point I got the mysterious grey screen of death.
I upgraded to 11.7 drivers but that didn't help.
MOBO: Gigabyte P67A-UD4-B3
CPU: i5 2500K @ 4.5Ghz
RAM: Corsair Vengeance 8GB
GPU: ASUS Radeon 6970 DirectCU II 2GB (Overclocked to 950/1440 only when playing games)
OS: Windows 7 64-bit
It does that with flash, I'm not sure about other forms of media. If you turn off hardware acceleration, that stops. 5.8Ghz on the ram is due to DDR5 running at 4 times it's clock speed. So 1450mhz memory clock will run at 5800mhz or 5.8ghz.
Just save your settings and try them at stock. You can always go back if it doesn't help.
I've read about people having troubles with the 6950 cards after flashing to 6970 when following the results after people flashed. It seemed prolonged use at memory settings beyond stock could cause them to be damaged. It could be the memory overclock on the card caused permanent damage.
Did you change anything in your system over the past few months? Did you try with both CPU and GPU set to stock settings?
Here's some interesting information that might be useful:
I put the computer to sleep for ten minutes while I made a a cup of tea and when I pressed the power button to wake it up, the fans whirred up but the monitor received no signal and my keyboard and mouse weren't receiving any power. I pressed the reset switch which shut it down but didn't automatically power it back up.
This might be a long shot, or even a coincidence, but when my network adapter is under load trying to open a few websites I get constant playback choppiness. Once I disconnected from the network everything returned to normal. This would explain the problem starting when I upgraded my router.
Edit: I just played through a mission of Mass Effect 2 with the network connection disabled and encountered absolutely no issues. I guess it's time to restart this thread in the appropriate forum.