Even though this thread has a best aswer selected, I thought I might chime in.
What is you r motherboard?
If it is an Asus P6T, here
is a video of setting that [H]ardOCP did.
I followed it, and ran at 3.8 fine!
Even if your mobo is not as Asus, maybe you can get the settings. I googled it and found 2 very good sites with settings. The above is one. The other is very detailed.