My Build is giving me pains

I've been working on putting together a budget gaming machine. My components are pretty basic but should run what I want them to: Antec Basiq 500W psu, GIGABYTE GA-M57SLI-S4 AM2 NVIDIA nForce 570 SLI MCP ATX AMD Motherboard, and AMD Athlon 64 X2 3800+ Windsor 2.0GHz 2 x 512KB L2 Cache Socket AM2 89W Dual-Core Processor. (If you need me to list more components in order to solve the problem, I can.)

I originally had a cheap, flimsy case from Linkworld (which I bought because I was already over budget but wanted lights and a side panel window). The first one I ordered broke in transit; Newegg replaced it with no argument. The replacement was OK at first, and I was able to get the computer turned on--twice. Here's where the question is.

I couldn't get the computer to turn off again; I had to use the switch on the PSU instead of the button. After a couple of startups (just my attempts to get the thing running, make all the fans and LEDs work, etc) it ceased to respond to the power button, and all coaxing was of no avail. We used a multimeter and found that there was no difference in the resistance in the wires going to the power switch whether it was depressed or not--suggesting that something was jarred loose in that circuit?

Well, OK, replacing a $22 case isn't so bad. Newegg gave my money back and I ordered this one instead. Everything seems to be hooked up properly, but it still doesn't react when I push the buttons. (Standard PEBKAC rebuttals--yes, it's plugged in; yes, the wall socket has current running to it; yes, the power switch on the PSU is turned on; yes, the connector from the power button to the mobo is hooked up as specified in the user's manual).

I don't think it's the psu, as we also tried using the crap PSU that came with the case, to similar effect. According to the reviews, it's usually good for a couple of boots, anyway. We've quadruple checked all the daisy chaining; nothing.

Should I be looking for new and exciting ways to hook up the power button? Should I be exploring every cavity with the multimeter? Should I be crying in a corner? Any help would be appreciated.

-Hannah G.

OK ... Could defective wires in the old case have done something to the power switch connectors on the mobo? This board has lots of good reviews, so I can't assume that all Gigabyte boards of the same make will have the same problem, right?