The board revision LF R29FA v1.0 4GB is the exact same board used in Powercolor's current R9 290x cards: http://forums.overclockers.co.uk/showthread.php?p=26900763. I wonder if the 390x bios could be flashed to the 290x :)
Probably a pointless question, but is it overclocked? I had the same problem when oc'ing using AB/Trixx, stable in games but sometimes driver crashes when running media or when launching BF3. Trying using stock settings or only CCC now to see if it helps...