ok i think i got ur solution. Idk how to adjust msi bioses, so if it is something simular to that im gonna tell u now do it. Go on bios, in the cpu setting and set ur Advanced clock calibiration to Auto. IF u can't find it install Amd Overdrive and i will tell u the instruction, give me a quick reply so I can help u before I go.
Go on preference tab and mark the advanced mode in perfomance controle mode and apply. After that go in Perfomance tab and click the clock/voltage. There u will see Advanced clock calibration. (Default is disabled) Change it to Auto, if that doesn't effect change to All Cores. I hope this helps . if u dont understand how to do this 100% i could send pictures Dont forget to restart after the setting!
I tried to Google to find any others who has this or had this problem. But no one has. By the way, have you checked the task manager. I recommend i to crosscheck it. Right click on ur desktop bar and choose task manager, then go to perfomance. If it show 4 windows, all your cores will be running. If not, then i cant help you more sorry
Run msconfig.exe (either from the start search for vista or 7, or from the "run" dialog in xp). Under the boot tab, click the "Advanced" button. Make sure the "Number of Processors" box is unchecked.