It is quite possible. Heat is pretty much the enemy of any computer. I never did quite understand why most mobo's put their AGP slot RIGHT UNDER the CPU socket?!
Another suspect would be your power supply. I love AMD's, and will probably never own a different processor than, but they are power hungry and don't like to share. Unfortunately, the graphic card is JUST as hungry and doesn't like to take no for an answer...
I'm paranoid so I bought a 450watt supply (I've just a 1.3ghz) A bit pricy (apx $59+) but it might help your cause...that and either some more fans or do like me and just take off the side panel of your puter...(be wary of pets and stock up on canned air)...
On a side note (not sure if it applies to you) but if you have a add-on Firewire (1394, I-link, whatever) card, make sure it isn't too close to the graphics card. Little known, but firewire cards tend to build up a static charge and have to be 'discharged' every now and then (just disconnect the card from the mobo, wait 30sec, and re-connect). A longshot, but it tends to artifact (sparkle) captured material...*might* account for your GC behavior...
Just some possibilities...
"Eagles May Soar, But Weasels Don't Get Sucked Into Jet Engines"