Did you keep the ram in sync with the FSB so 425FSB (1700) ram at 850 then or did you force to get 1066Mhz ? if so that doesn't work with me I need to keep it in line same for 450FSB needs 900 ram speed not 1000 nor 1066, it's due to a limitation of the 680i chipset bundled with a quad I think...with a dual core CPU I can fool around with the ramspeed as much as I want...

On a german forum found that 412 FSB also works so 1648FSB (also with 9 multi to get 3.7ghz), 1700 should be doable ( have you tried also with 8 multi to get 3.4ghz instead of keeping it locked at 9 multi) as many many users (on older boards too) have found this to be perfectly stable, 450FSB though is hit and miss...