Yup upping your ram v should do it that was all that really held me back. I had to up HT and Northbridge voltage a tiny amount before it was stable on my MSI K9A Platinum. Vcore is at 1.54.
HT is linked fine @ 1140 Mhz and so is RAM @ 427 Mhz 1:1 (fairly cheap OCZ). You should be able to tighten ram timings aswell, mine were 5-5-5-15 now 4-4-4-15. Temps are all fine with a Thermalright 120 Ultra and AS5 so with watercooling sure you'll have no probs. Now getting 24 seconds 1m Super Pi as opposed to 30 which was mine at STD.
As some of the above have already said, if this doesn't work try lossening ram, lowering HT multi or change ram ratio. Not much else I can think of I'm afriad. Oh maybe turn off spread spectrum if not off already, it can help stability.
If you get passed 3.4 Ghz plz do tell i can't get mine past 3.42 mainly from heat, I don't really like near 50 C showing up on load. There's not been that many ppl talking about the 6000+ heat ranges. I know intel can have HOT cpu's coz many people ask for help o/cing them, but very few have or care to talk about their 6000+ overclocking experience.
Does anyone know what temps AMD's X2 are happy at? Anyway I hope my experience with this cpu helps.