Athlon II X3 425 Unlock to Phenom B25 Changed on it' own!

[siliconsy]

Hi, as I'm sure most of you are aware many of the AMD K10 family of cpu's are potentially unlock-able (http://www.cpu-world.com/info/AMD/Unlocking_cores_and_L3.html)
I have an Athlon II 425 X3 (http://www.cpu-world.com/CPUs/K10/AMD-Athlon%20II%20X3%20425%20-%20ADX425WFK32GI%20(ADX425WFGIBOX).html) that has been working perfectly for about a month as an Phenom B25 X4 with no problems other than the expected lack of core temperature sensors.
The odd part is I didn't do this! The power button on my pc jammed in for about 20 seconds, when I released it the there was a bar below the bios post saying "4th core unlocked" and sure enough once booted up, there it was. I've reset the bios to default setting numerous times in the past and this has never occurred before (as may have thought jammed button had simply flashed bios caused it) I have no software that's automatically updates my bios when a new version is available (don't think win update covers bios) so this is not the cause either.
Has any one else had this or similar happen to them?

[Thandor]

Which motherboard do you have?