Highest strap available on this board is 266. So your saying in order to run your memory @ DDR2-1000 you have to set the memory settings to auto or normal. Fast doesn't work. Fast if I understand it correctly sets some tight internal latency's etc., which makes the board perform alot better. This makes me more inclined to believe this board is memory picky.

Rattle, do you have any other memory other than those firesticks you can try out? Well at least you got 500FSB stable. I'm been playing around with 500FSB & Pi with some old fatbody's 4-3-2-4. Trying to see how tight I can get everything. Gonna have to swap to the 6600 for the 4mb cache though.