I've been looking around for threads speaking of the same problem. I found a thread on another site describing how a new BIOS was preventing him from overclocking to 3.6Ghz, while an older BIOS version worked better. You can find this thread here
While again the board in that thread is an Asus board, I thought it had a chance of also applying to my board. Could this also be my problem? If so how could I downgrade my BIOS?