Question about unlocking cores

My MB is a MSI 880GM-41, and i am trying to unlock the fourth core in a Athlon IIx3 450 Rana 3.2ghz. The MB is allegedly pronounced to support the unlocking feature. However when I try to unlock it in the bios, I save and exit and then the computer shuts off, starts back up, but does not boot up. I have tried restarting multiple times etc. etc...... But I end up having to manually go into the case and removing the battery on the MB to get a total reset. Am I doing something wrong? or will this core just not unlock? Once again allegedly, core unlocking is supported with this CPU.....? Any ideas or help would be greatly appreciated