Updated the BIOS to F7 with the built-in updater, now system stops without
warning anywhere from a few seconds to about 10 minutes after boot. Power
supply must be turned off for a while before system will restart.

SIV utility shows CPU temp 52C, system temp 42, CPU and case fans 4200rpm,
voltages OK.

Not sure the BIOS had anything to do with this, this is the first time
system has been turned off in a long time and it's been running almost
continuous 24/7 for over three years. No problems prior to this.

Athlon 1700+ CPU, 1 512MB DDR, Antec 303XP power supply.

Anyone know a likely cause for this problem?

thanks,
nf