[Cube] The infamous Cube shutdown problem

[Tom Burns]

Hello, Cubists! 

Just got a Cube (my second) though an Ebay auction: G4 Cube, 640 MB RAM, 1.6
MHz upgrade, cooling fan, running OSX Tiger.

>From the first boot, it manifested the cursed shutdown/ reboot problem that
I gather is common among Cubes, but mine seems particularly problematic.  It
sometimes reboots or shuts down during startup.  When I try to start up from
the system DVD, it takes so long on the diagnostic stuff at the beginning
that it shuts down during the "spinning wheel" stage of the startup.  After
a couple of tries, it gets to the finder, but it simply shuts down
completely and without warning a few minutes later, no matter what software
is running.  It's like somebody turned off the power.

The seller says he never had the problem before he shipped it to me, and I
believe him.  (He seems like an up-front person.) I've tried making sure the
various memory sticks and boards are secure in their slots (at least the
ones I could reach without disassembling the machine).

Any suggestions? If I have the infamous "power-switch-gasket problem," I am
at a loss on how to fix it.  I've tried the usual Mac parts places, and the
gasket doesn't seem to be available any more. Does anybody know of any fixes
to the gasket (if that's the problem) besides replacing the gasket?  Do the
symptoms indicate another problem?

Otherwise, this is one kickin' machine.  I'd hate to lose it.

Cubistically yours,

Tom B.