Something is obviously wrong. I had a my 965P-DS3 rev 1.0 and Q6600 B3 combo running at up to 450FSB 1:1 with the memory without any issues at all. If you are using the JMB36X controller for your hard drives then make sure you have set it up appropriately and installed the latest drivers. The other thing that can stop you is using windows utilities for FSB clocking and innapropriate memory settings. Try leaving the memory on auto timings 1:1 with the FSB and boot at FSB intervals of 20MHz when you test for max FSB. What revision is the troublesome board?