My Cube won't run Jaguar

[Michael Blossom]

Hello Cube Peeps, I need some advice.

OS 9.2.2 runs fine on my Cube, which I bought refurbished from Apple (no
AppleCare).  Well, I've had some firewire problems, but mostly fine.

I finally got around to installing OS X 10.2, and it doesn't work.  When
I click on an item in a menu in OS X, it causes the frontmost application
to crash about 1 out of every 3 times.  This includes the Finder.

This flakiness even happens when I boot from the Jaguar installation CD.

I have ruled out:

RAM (Same behavior with two different RAM cards, also different slots)
Hard drive (I've reformatted, and like I said it happens even when
booting from CD)
Installation (I've reinstalled a few times)
Installation CD (Something an Apple tech support guy had me try
apparently ruled that out)
Video card (Tried with original Rage or new nVidia)

The Apple guy I spoke to gave up and told me to bring my Cube to CompUSA
for service.

Maybe I should mention my old FireWire problems in OS 9 -- I never could
get a MOTU 828 FW audio device to work properly, although it works with a
G4 Tower, and I get a lot more freeze-ups when a FW drive is connected to
the Cube.

If you were me, would you:

A) Take the thing to CompUSA and pay for repairs
B) Buy a new motherboard and try that ($199)
C) Upgrade the processor (seems doubtful it's the processor, and TechTool
Deluxe says it's ok)
D) Suspect the DC-DC card (but how could this cause a Finder crash?)
E) Part the thing out and get a used Cube on eBay?
F) Something else?

Thanks,
Mike