I'm sorry to have to tell you this but your card is most likely pooched. I currently run 2 XFX Radeon 4870 1GB in Crossfire and I have no issues with anything whatsoever. Well, the heat is annoying but with my twin Powercolor Radeon HD 7870 2GB on the way, that will be a problem of the past. My 4870s have been rock-solid for the 5 years I've owned them and they still are. I'm sorry but it looks like your 4870 has reached its end-of-life. If you have an XFX card, it's under lifetime warranty so that should help you out. My Powercolors only have a 2-year warranty but let's face it, if they don't die in the first 2 years, they'll last a LONG time. Even if they don't, I'll still have my 4870s safely stored away for a rainy day if anything happens. NCIX currently has an unbelievable deal on the HD 7870 ($140 after rebate) that undercuts even the cheapest HIS HD 7850 that I found on newegg. Good luck to you!