10.4.8 Update iMac20 Panic/Dump/Hang

Question

I'm a new mac user and responded to the automated update of 10.4.8 (from 10.4.7 --among other updates), my system hung and now concludes its boot with a panic dump message something like...
-panic (cpu 0 caller 0x003A8DBD): Unable to find driver for this platform: "CPI".
-Debugger called: <panic>
-Backtrace, Format - Frame : Return Address (4 potential args on stack)
- (bunch of addresses & contents (i.e. hex))
-Kernel version:
Darwin Kernel Version 8.8.1: Mon Sep 25 1942:00 PDT 2006; root:xnu-792.3.8obj~1/RELEASE_I386
I unplug everything except the keyboard and ethernet..., same result.
...Bad timing. I'm leaving on a trip in 8 hours and desperately need this system functioning.
Thanks to anyone who knows how to "back out" of this update suite or repair what's wrong.
Frank Gossett

Answer 1

Thank you Brody --and thanks to MacJack for the reply to a similar 10.4.8 upgrade poster (i.e. Disk Utilities procedures).
I've run procedures MacJack suggested with the distribution disk (Disk First Aid) with the following results...
1.1) panic dump problems after upgrade from 10.4.7 to 10.4.8: Repair attempts:
1.1.1) Action: Attempted safe mode boot
Status/Result: Panic/dump interrupts reboot process.
1.1.2) Action: Booted MacOSX distribution disk and ran Disk Utility->Repair Disk Status: One error was repaired.
Result: Panic/dump interrupts reboot process.
1.1.3) Action: Booted MacOSX distribution disk and ran Disk Utility->Repair Disk Permissions:
Status/Result: Multilingual “Must restart…by pressing power…” widget interrupts “Repair Disk Permissions” process ( NOT the panic dump as before… )
1.1.4) Action: Booted MacOSX distribution disk and ran Disk Utility->Verify Disk Permissions:
Status: “Permissions Differ” message… on files… ./Library/Printers/EPSON… (approx 150 files or so), ./Library/Widgets (1 file), ./System/Library/Extensions/ATIRadeonX1000GA.plgin/Contenets/PkgInfo (1 file), ./private/etc/authorization ( 1 file ), ./usr/bin/fetchmail ( 1 file ) and ./usr/standalone/i386/boot.efi (1 file). Finally the output of disk repair is “…Privileges have been verified or repaired…”
Result: (No reboot until completion of step 1.1.5 below)
1.1.5) Action: Disk Utility->Repair Disk Permissions:
Status: “Permissions Repair Complete” message with… a lot of files with permissions corrected –including ./private/etc/authorization ( 1 file ) and ./usr/standalone/i386/boot.efi (1 file).
Result: Panic/dump interrupts reboot process.
1.1.6) Action: Apple Hardware Test (Extended) …Thanks Brody!
Status/Result: a) Test Results: Alert! Apple Hardware Test has detected an error (4MEM/4/40000000: 0x7c66f090)
b) The machine was locked up after encountering the memory problem.
I know this sounds crazy, but... does this mean that there is positivily a memory problem or could this be the result of cascaded anomalies?
Thanks to all who have made suggestions so far.
Frank