I too have noticed some sort of "hole" around 400/1600fsb. At least for my board. If I can get into Windows, everything seems good and stable. However, once every five restarts or so, I just get a blank screen and no POST. Hitting the reset button brings it back at fail-safe speeds via OC crash recovery mode.

Intel E8500 w/ Thermalright Ultra-120 Extreme (no OC yet - Stability Testing)
GTX 280 SLi (eVGA)
4GB Mushkin 1600 DDR3 7-7-6-18-2T (WinXP 64-bit)
Asus Striker II Extreme BIOS 0901
300GB Velociraptor
Creative X-fi Titanium PCI-E
Thermaltake Toughpower 1200W