G4 tower won't turn on

My Mac G4 tower / 733 was working fine. I restarted and the for a while it just wouldn't boot. The symptoms at that time were:

At powerup:
Power light comes on
Fan and hard drive spin up
chimes
and that's it

nothing on the monitor
keyboard combinations (like zapping p ram) do nothing

So I tried opening it up and reseating everything, removing the battery, and hitting the motherboard reset button. And now all it does when I try to power up is the power light on the front of the Mac flashed once and that's it. No other activity from the box at all.

Anyone have any ideas what's wrong with my baby?

Thanks,

~ Adrian