Posting from a 7 year old CRT and ugh, now I know why I thought I needed glasses back then. lol.
I tried the changing the lead to the monitor. Turned it on, blue light flickered(no orange this time) for about 5 seconds then shut off. Stayed off after that.
Yes, it turns off fine. And I've checked and reseated the wiring twice already.
Try connecting the switch wiring to the reset pins and see if that also works. Obviously, if you have another case handy, just wiring the switch in to the motherboard and testing that would tell you a lot also. Depending on how much time you want to invest in this, take the motherboard out and see if something's come loose on the back of the pcb. Of course, by then, you could have just bought and installed a new motherboard and case for $150 or less, so there's a real question of just how much you really care about this and what finding a solution is worth to you.
It's not rocket science, though, it's either the case switch, the board/switch interface, or some catastrophic CMOS failure. Unsynch your OS clock from a timeserver and see if it's "losing" time during the time you can't switch it on. If it is, it could just be a bad CMOS battery/chip, which would prevent the BIOS from starting at the power signal (and would also explain why when you leave the power switch on it would randomly start up after an hour). You could try replacing that. The real problem, in my eyes, is that we're talking about an essentially disposable item at this point. You haven't listed your MB specs but it's likely, given your CPU, that it's cheap to the point of spending more than an hour on this is a waste compared to just replacing it.
You follow me? You don't spend 15 hours repairing a leak in a $25 tire, you just buy a new tire. If you just want the "win" of fixing it, or you really don't have the $50 or whatever, I understand, but from a utilitarian standpoint you're verging on wasting your time.
This is my motherboard right here: http://www.newegg.com/Product/Product.aspx?Item=N82E16813130057#spec
Just over a 2 year old computer, costed 130$ at the time. And the CPU 160$. >_> lol. Haven't upgraded it since then because of no need. Originally built it for FPS but now I'm more into MMOs which aren't nearly as graphic intensive.
But I understand what you're saying though. I was more worried about the (now dead) monitor than the power on issue. It's just a minor inconvenience to me really since I rarely turn the PC off completely. But I figured I'd ask to kill 2 birds with one stone and to find if there was a potentially serious problem behind it, which from what you're saying is not the case.
Thanks for the help, both of you.