G4 Digital Audio... froze and won't boot.

Single processor 800 MHz with 1.5 of memory, I'm running OS 9.2 so I can use my MOTU 2408 MkII with Digital Performer 3. I went to lunch and when I came back all the green lights on the MOTU bottom row were on(?) and the monitor still had the project up. There was no response to keyboard commands, so I powered down and waited. The power button lights and then goes off, evidently there is power to the motherboard since the red light is on, the fans work, it sounds like the HD's are doing their thing, the green lights are on on the SCSI board but nothing on the monitor, no chime, and the mouse doesn't light up, apparently the G4 is not responding to keyboard commands either. I tried the CUDA, pulled and tested the battery, left it sitting overnight, prayed,so far I haven't found the problem. I found another G4, except it's a dual processor, so hopefully "after all this is over" I'll have a back up system. Is this a video card problem?