If your basic RAM setting is on AUTO, you may be trying to verclock your RAM and that is limiting your CPU overclock.
Try changing the System Memory Multiplier (or whatever your BIOS calls it) from AUTO to 2.00, 2.00B, or 2.00D - whichever you need to set the Memory Frequency to twice the FSB. Then when you increase the FSB, the memory clock will rise in step with it. If you are at 3.0 GHz (353 MHz X 8.5), your memory clock should be at 706 MHz.
Download CPU-Z to check your FSB:RAM ratio.
Warning - confusion factor between what the BIOS calls things and what CPUZ calls things. What the BIOS calls "memory frequency" is actually the memory clock. What CPUZ calls "memory frequency" is half the memory clock - DDR2 RAM, remember? It transfers two chunks of data each bus cycle. What you want in CPUZ is a 1:1 FSB:RAM ratio.