ga-m55plus-s3g memory problems

[Spliff]

Firstly, I apologize if this has been covered previously, but I searched and didn't find anything specific to this MB, I recently tried to install Crucial 2x2gb ddr2 6400-800mhz in this MB, with both installed, no boot, tried slots 1+2, then 3+4, same result, tried each stick individually in slot 1, and both boot machine fine in single channel mode, but not together. I've flashed to the latest BETA bios, wondering if that might be the problem, also have tried tweaking the ram voltages all the way up the line, with the same no boot results.