I have a Dual Processor 500Mhz G4.
The only disc it will boot off is 9.0.4
I've tried booting off a 9.1 disc, an OSX (10 & 10.2) disc, Norton Utilities 6 disc.
Even if I install 9.0.4 and try and upgrade to 9.1 - the mac crashes when I try to run the upgrade installer.
Basically looks like this machine doesn't like anything above 9.0.4!!
It runs fine under 9.0.4 with Logic 4.8.1, MOTU PCI-324, Adaptec 2940UW, MOTU MTP AV.
I've stripped everything out of the machine, even swapped out the RAM as I heard this might be an issue.
Back to the bare bones of Monitor, Keyboard, Mouse and 1 slot of RAM;
no joy. I've used my OS CDROMs and borrowed discs from friends thinking my disks might be damaged so dodgy CD's are out of the question.

HELP!

When I upgraded from an 8600 to a G4/400 I had to ditch my 2940UW. It would not live with my audio and video cards. Especially my second ATI card for dual monitors.

I installed an IDE drive and all is well. Tested 50+ 16bit mono tracks.

Check the Apple and Adaptec sites for more info.
I was also under the impression that Adaptec was dropping Mac support.

Try removing the 2490 and installing the OS.

Thanks for the reply.
I've stripped everything out of the machine... no joy.
As I said, it behaves itself perfectly under 9.04 but as for upgrading...

Anyone else any ideas?

You didn't mention a 9.2.2 install CD. If you did borrow one, could you boot from the CD. If it did boot, I'd say you've got an extension conflict. Try scrapping your prefs IF you've got all the info you need to build them again.

I've no experience with your gear but I've had macs for yonks, and any probs I've had have been due to extensions or prefs and never to the hardware.