Ok, have you tested each memory module individually in each slot? you need to figure out if you have been unliky and got 2 memory sets with a faulty module. At the same time whilst doing this, if you get it where there is a specific slot that is causing the problem then yopu know it is the motherboard. Out of interest what slots do you have teh memory in?
If after this it is still not obvious that either memory of board is faulty you will need to test another CPU or your cpu in another board, as the CPU has the memory controller.
Also as a side note, teh deafult speeds of the RMA with the BIOS settings at default should be 1066.
hope this helps