I've just updated BIOS of my Asus P5GD1 from 1013 to 1014 and my PC was able to power off as expected. Damn it! It was the first thing I've thought a year ago, when I've discovered this bug. At the time I've seen BIOS update 1014 at support.asus.com that only "Support new CPUs". I've had (and now have) P4-630, that according to Asus was supported from 1007 BIOS revision. And Windows XP was able to power off my PC even with 1013 BIOS. I don't think my next motherboard will be Asus...
I've just updated BIOS of my Asus P5GD1 from 1013 to 1014 and my PC was able to power off as expected. Damn it! It was the first thing I've thought a year ago, when I've discovered this bug. At the time I've seen BIOS update 1014 at support.asus.com that only "Support new CPUs". I've had (and now have) P4-630, that according to Asus was supported from 1007 BIOS revision. And Windows XP was able to power off my PC even with 1013 BIOS. I don't think my next motherboard will be Asus...