Multiple(?) BIOS passwords

Hi.

Since long I seem to have multiple(?) BIOS-passwords on one of my PCs.

Every major update of either Norton 360 or Windows operative (Vista and Win10) it refuses the correct password. I always have to retype it (and, yes, it is the correct one first time).

I have never set a different BIOS password than the original one - so, why this behavior?

Norton Power Eraser or Full system scan never finds anything. I have also set Norton 360 to aggressive boot.

Is there some security-item that hooks on earlier than NPE or Norton 360 (aggressive boot) - something like the renown IceSword - that is able to detect/remedy this problem?