Computer freezes on boot when restarted.  Will only work if I disconnect the power supply. - NOT THE POWER SUPPLY

Here are the system specs:

Abit AT7 MAX motherboard
512 MB DDR Memory
Generic PCI Graphics Card
Antec 350 Watt PSU

Here is the problem:

Just recently, one of my clients computers went down.  It was a hot day and his secretary remarked that the office smelled like somebody had burned something (no burn marks on any of the hardware that I can see).  When I pulled the box and tried booting it up in my office, all the fans spin up, the LED's come on, but nothing else happens.  The monitor doesn't come on.  The mouse and keyboard don't light up.  Dead.  So I went about swapping everything out with working devices and still no luck.  Hard Drive: Works in different computer.  Graphics Card: Works in different comptuer. RAM: works in different computer.  I purcahsed a second power supply hoping it was the problem maker.    Well, the computer boots now.  WOOHOO!!  So I go about putting the machine back together thinking I solved the problem (Too easy right?!)  I boot up, success.  Windows boots just fine.  We are in windows.  Everything runs great.  I'm feeling good.  I do a reboot after making a small change and the problem arrizes once more.  The system goes through the shutdown process everything goes down just fine.  Then the monitor light comes on, but thats it.  Blank screen.  No keyboard or mouse lights.  What is going on?!  I press the retart button.  Same thing.  Green monitor light but nothing on the screen.  So I hold the power button down for a full shutdown.  When I press the button again to boot up the green monitor light comes on and then nothing, again..  So I pull the power out of the power supply and let everything discharge for a moment.  Plug it back in, reboot, and voila, the machine is up and running again.  I do these tests several times and I have come to the conclusion that: I can only turn the computer on by unplugging the power from the power supply and replugging it back in.  This is obviously not going to fly with my client.  As I mentioned earlier, I purchased a brand spankin' new Antec 350 watt power supply that should do the trick no problem.  Oh, and I have flashed the CMOS for those of your curious.  So I am at my witt's end.  Do any of your fantastic people have any ideas as to what the problem is?  I fear it is the motherboard, which is relatively new :\ .   Any help or suggestions will be greatly appreciated.  Thank you.

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