Hd4870 red lights of doom

So I'd been having a problem for about a week where my system would crash shortly after opening most programs due to various kinds of memory errors. After quite a bit of research, I finally figured out that it was most likely because my motherboard (Intel DP45SG) defaulted to supply 1.54V to each stick of RAM, but the RAM was supposed to get 1.7V.

Fixed that in the BIOS and the system worked fine, ran Crysis indefinitely with no problems, etc.

Next time I tried to turn on the machine, though, I got no video and three blinking red lights on the back of my graphics card. Seems that happens when the card is not getting enough power.

I opened up the case and checked, and the mobo, video card and CPU are each on their own 12V rails; I have a relatively new NZXT 800W power supply, so I seriously doubt being underpowered is the issue.

Could this be some kind of issue where the board or card thinks something is overclocked and power is getting diverted? If so, how do I fix that? Keep in mind, this is not an overclocked system; I just had to manually go in and adjust the RAM voltage to give it the minimum requirement.

Specs:
Intel q9550 2.83 gHz
Intel DP45SG motherboard
4x2GB Patriot DDR3 1333-10666 7-7-7-20 RAM
Radeon HD4870 512MB