I've had NO END of problems with a mates A7A266.
Firstly are you using Micron/Crucial RAM??? if so, this may be a cause of the problem. some modules that they produce are not compatible..
Secondly, to alleviate this problem, try removing the "mystery jumper" which is beside the AGP, which allows more current to the RAM and may clear the problem.
so far I have had to replace 2 of these boards, but the guy at DABS.COM support assured me that they had sold at least 1000 boards, and only 4 had come back.... a load of crapolio methinks.... maybe third board lucky eh...