here ya go... i think the 3.3v int is the video card's memory voltage? i'm not sure. either way its more watts and amps, but on a diff rail all together.
http://www.xbitlabs.com/articles/video/display/gpu-power-consumption-2010_3.html#sect0
the bar graphs are showing the measurements in watts, while the charts have the amp info
back to the O.P.'s issue... have you tried forcing the fan speed to max at all times? this would (in most cases) solve any overheating issues, but make a lot of noise sometimes. If it solves the issue, then you need to find an aftermarket cooler, or not if your ok with the sound.
inspect the cabling for any exposed wire or "pinched" areas. copper can only bend soo much before it breaks, and if there are breaks in the wire the resistance increases making it harder for the card to get its power.
If you're feeling adventurous, switch the psu off in the back, and press the case power button in the front. you may see the fans spin up for a sec, this is normal as its draining out any built up power in the caps. Now you are safe to take the psu out of the computer and open up its case, don't worry i'm not talking about messing with the wires... just clear out any dust you see on any components. also while your at it, turn the fan with your finger and check for resistance... if its sluggish to turn then it may be going out and not as effective. you can replace it with another 80mm (or w/e sized fan it has) by cutting the wire, and wireing the new fan in (sometimes your lucky and you can use the plug)
inspect your video card carefully, check for bulging caps. if you can take off the blower cover and clean the insides out good. if the memory chips are cooled via thermal pad making contact with the main heat sink, new thermal pads wouldn't hurt, but not really needed. the gpu could use some new paste though. clean the gpu thoroughly and carefully. when applying the new past you only need about the size of a grain of rice and spread it with a credit card or the like. when re-attaching the heatsink (also clean the heatsink base, you can even get a fine grit sand paper and sand it smooth if you want) gradually tighten the screws from opposite corners, about half turns at a time.
to rule out anything else, have you ran any thorough memory and cpu tests on the rig? do a spyware/virus scan too, those nasty critters can do the strangest things to drivers.
