no neda sa to jednoznacne urcit, problem bude v nejakom hardware.
horsia varianta: moze odchadzat motherboard
lepsia varianta: nejaka nekompatibilita s novym hardware(moze pomoct flash biosu), alebo corruptovany bios. flashom nevej verzie nic nepokazis. dobre je si ale staru verziu odzalohovat.
na nejaky povytiahnuty kablik to netipujem, to by najskor nehlasilo checksum error.

toto je taky standard:

Diagnosis: The most common cause of checksum errors in CMOS is a battery that is losing power. Viruses can also affect CMOS settings, and motherboard problems can also affect the stored values.