I highly doubt it's a power issue. I'm running a window AC unit on outlet just below the one that has my power strip for my computer stuff on it and the AC unit runs perfectly (and there's no change even when the AC unit is off).
damn dude! Ever consider that you AC unit might be drawing the majority of the amperage coming out of that outlet? if you don't have a solid, steady current of electricity coming into your powersupply you are running the risk of frying a lot more than just your video card.
Try invsesting in a UPS (uninterupted power supply). They are designed to hold a charge so that if your outlet power fluctuates, the stuff plugged into the UPS will still have a steady flow of electricity.
Don't right this off as "i doubt that". You could very well have a serious power issue.
I troubleshoot cash registers for my job. I run into this issue at least once a month. For the 80 bucks your gonna spend getting a UPS its worth it. Most of them also have a warrantee so if any of your hardware dies do to power issues, they will replace it. I believe APC covers up to $10k for failed equipment.