Try 2,7 Volts as well ,it s ok.
What 3Gigs of RAM mean ,how many sticks ?!
If more than 2 sticks expect the speed to be 266Mhz.
With 1/2 sticks you may achieve higher.
I have had in the last 3 years Kingston memory and it never worked at the stated speed with more than one stick from a kit installed.
try detting your ram at unganged nad se if it helps.
Ganged/Unganged appeared along first Phenom release ,there is no such setting in his system.