I've seen situations such as that. Working outside the case, but not in the case is usually points to a short of the motherboard through the case (of course, assuming it is wired correctly).
As I recall, it took me a considerable while to determine that the equipment worked outside the case. I think I tried replacing the RAM, CPU, and PSU before doing the mobo, and unless you have an idea that the case itself might be the issue, well, why would you take the rest of the machine apart? And even if you suspected a board short, you might easily be misled into thinking that it was a part of the case touching the mobo inappropriately, and leave the reset/power leads connected: it's a lot easier to punch the case reset button than to use the tiny one built into the board. And of course, figuring out that the system works without the power switch connected is not super useful in itself: that is something of a necessary component.
I'm just still amazed that he figured it out that quickly; I really didn't tell him much about what had happened, and I'd hardly had time to leave the room before he'd solved it. What a jerk :)
I'm just still amazed that he figured it out that quickly; I really didn't tell him much about what had happened, and I'd hardly had time to leave the room before he'd solved it. What a jerk :)