I upgraded to Ubuntu 8.03.  Now, during the post-boot initialization process the system goes into a fugue trying to  mount the CD/DVD drive.

It keeps trying:

ata2.00: Exception Emask 0x0 SAct 0x0 SErr 0x0 Action Frozen
ata2.00: cmd a0/00:00:00:24:00/ et cetera
ata2.00: status {DRDY}

So I try to use the CD of Ubuntu 7.10 that came with the Dell system as a rescue disk.  Unfortunately, it won't play nice with something in the video stack (probably the monitor).  It comes up in VGA mode, but when it comes time to run the boot or install option, video won't work and keeps complaining about V60Hz and H74.6Hz.  (I don't know if it's the monitor or the OS complaining about the video synch frequency.)

So:
I can't boot from hard drive.
And I can only boot to ram drive from the "rescue" CD.

I'm thinking of opening the box and disconnecting the CD/DVD to see if that will result in a boot.