System,error,critical

my x86 routerOS system restarting and I’m getting this error:
system,error.critical - system reboot without proper shutdown.

the configuration is:
Dell precision T3400
C2D 2.6Ghz
2GB Ram
1x PCI express Intel Pro dual interface ethernet card
80GB Sata 2 HDD

the cpu load is low (5~20) and the traffic is usually 15Mbps to 30Mbps

any ideas about that?

thank you!

routeros version? packages installed ?

I would first check motherboard and power supply for faulty capacitors. This error indicates that the reboot was due to power outage.