I have an 8600 as well with a 1.7M. It's about 3 months old now. I would have this turn on problem whenever I would flash the BIOS. It seemed to need to cool down, then it would start back up. Subsequent reboots would be fine. I contacted Dell about this, and after the tech in India asked me to try something that wasn't even possible on an 8600, I asked for a service call.
A very competent tech came and swapped the mobo (in less than 20 minutes). The replacement mobo was at A03 BIOS level, and current is A08. Since then, I have only had the green light no boot two or three times. I just press the power again and it comes back up. So not like before. I have the 3 year warranty @ home, so I will be sure to use it if it becomes a problem again.
This short story long explanation just seems to bear out that there is something fundamentally chronic here. This behavior is spanning generations here, and that's not good. Mine seemed to be more heat related, but ... If anything it seems like the new 8600C systems are worse?
- Dieter