Ok.
Beekeeper, I don't think you are understanding what Stillyan is saying.
Stillyan is unlocking two extra cores on his 550BE.
One of the unlocked cores is bad and crashes the system.
After unlock, the unlocked "bad core" is reassigned to either Core 0 or Core 1.
You can't disable Core 0 or Core 1 with the current CPU Core Control option.
No matter what arrangement of numbers for Core assignments gigabyte or anyone else uses, it stands to reason that it should be possible to disable a previously locked core on your processor.
I have the exact same problem on my system with my 550BE. The CPU Control Option won't let me disable the bad core.