^ agreed. Most of the AMD boards come with a Core Unlocker tool to unlock x2 and x3 CPUs to be a x4... but in your case, if this tool has been turned on, it is possibly deactivating one of your cores.
Usually the first step with booting up is to get into the BIOS and tell it to load Optimum Defaults. If it won't, then clear the BIOS memory by unplugging your PC from the wall and removing the CMOS battery for a few minutes.
If these things didn't help and it is still being reported this way, you could have a defective CPU or defective board.