Thanks for the suggestion about temperature running OSX.
Here is what I have done all yesterday:
Since the computer was starting up fine, I decided to do a clean install of my main HD. I used my portable hd w. OS 10.4.11 to wipe the drive clean, repair, etc. Then:
1. installed OS9.2.1 no problem, installed OS 9.2.2 update, no problem. Started up normally.
2. installed OS 10.4.11 and all updates. No apparent problem. Had to install a newer version of Itunes, added my music library, all working okay. I reinstalled my specific software, including Photoshop and Finale, which have never caused any problems for years.
3. After being in OSX for so long, I tried switching back to OS9.2.2
The problem is there again. Earlier in the evening when I switched, it changed, but the screen messed up, then cleared up and finished. However, at the end of the evening, after going back into OSX, and switching, I got my dreaded grey screen with a grid. I just shut it down and stopped for the evening, frustrated. I left it to start up in the morning in OS9.2.2
4. This AM (9AM) I started it, and (I noticed there was no startup sound) got the same grey screen with grid. I tried restarting using my OS 10.4.11 disc, and it started up fine, and I switched to start up in OSX, all started up fine, BUT I still noticed I now have no startup "sound" like I did yesterday after all the new reinstalls. I changed the monitor resolution to a lesser one in case the monitor res. was too high for the OS9 change (though I never had the problem before). Then I switiched back to startup with OS9.2.2
I still got the grey screen w. grid. I tried restarting several times, and once it started to boot, but then the screen went crazy again and froze. I tried again and it went back to the grey screen w. grid. And, no startup sound anymore at all this AM. Yesterday, every time I restarted I got the startup sound, but not now.
When I had OS 9 only, all was good, and when I reinstalled OSX and other software, it was good. But somewhere down the line, the longer I was in OS10.4.11 I started having the problems, and now can't get into OS 9.
For George, I had put new thermal paste on the day before. Also, before I started this thread, I had taken any and all extra pci cards and tried w. the bare bones G4, but still got the screen.
So, somehow, being in OSX for so long screws up the ability to change to OS9, AND I have lost the standard startup sound.
Since the screen works perfectly fine in OSX, I don't think it is the video card, so I am left with the heat issue and the motherboard as the sources of the problem, right?
As it stands right now, I can boot up in OSX, but not in OS 9.2.2, and I have lost the startup sound since yesterday, after reinstalling OSX + updates.
I just now switched out my Sonnet processor and put back the original G4 450 mhz processor, but there is no difference, I still get the grey screen, no startup sound.
This so frustrating because it was all working so well yesterday, startup sound and all, until later in the evening, after working in OSX for so long. Now I am right back where I started from.