Strange power button problem on my G4 dual ghz

My G4 desktop has a predictably flakey power button.

The power button doesn't work, but if i unplug and replug the power cord then it'll work and the machine will boot up normally.

Then if I shut down and try it again the next day I'll experience the same problem.

I thought maybe the SAFT lithium battery had run down since I don't use this desktop as much anymore so I replaced it with a new one. This had no effect - everything is just the same.

I don't see what unplugging the power cord would have to do with the button on the front.

Any ideas on what's going on or how to fix it?

Thanks,
boze

Sounds like it's latching somehow, either bad logic circuit or the button itself is stuck.

what's to be done about a bad logic circuit? would that account for it working each time if i unplug it?