[allblue]

I have been browsing these forums for several years, and as someone who knows next to nothing about how it all works I have found some very useful advice and tips.. but now I appear to be in trouble and could use some assistance.
I have a 2 1/2 year old much loved iMac G4 800 running 10.3.9 with 512 ram. Last night I downloaded the latest security update from Apple (poss cause 1, although I repaired permissions before and after as recommended) and all was fine when I booted up this morning. After several hours there was a power cut (they do happen from time to time here - poss cause 2) but it booted up ok after power was restored with the usual delay while disk utility checks things over. Then the fun began.
I had taken a couple of large photos (c. 13mb tiffs) and was manually dragging them from the memory stick to my desktop (I don't use iPhoto so don't use ImageCapture) when Finder hung (Finder does seem to crash quite frequently on my machine handling image files) - but hung good, because Force Quit could not touch it. After several minutes I had to reluctantly turn off the power and restart that way. It managed to start up albeit slowly, but when it got to desktop it managed the picture and dock, but there was only the menu bar shadow and no menu bar itself. I turned off and restarted again, and after an age desktop appeared complete. I breathed a sigh of relief and inserted the OS install CD to run disk repair, set it as start-up disk and restarted.
After a flat grey screen (no Apple logo) I got a screen I had never seen before - Welcome to Open Firmware. At the top it says
Invalid memory access at %SRR0: c3c3c3c0 %SRR1: 400003030
The two options offered are "shut-down' or "mac-boot" - the former does what it says, but the other gives an alarming maroon colour screen for a few seconds before reverting to a dark grey screen with what looks like a Classic folder with the finder symbol on it. I have tried this a few times, and sometimes the folder would have the old dreaded flashing question mark before the finder symbol, but none of it is much help for me.
So that it was I am left with, I can only access the open firmware screen, and the install cd is in the unopenable tray. I have tried both command-c and command-s at boot-up to no avail. One other point, on one occasion the open firmware message mentioned illegal USB access (unfortunately I did not take a note of the exact phrase) so it unplugged the card reader when the machine was off and that message disappeared to leave the one above.
So I have had to turn to my trusty old G3 333 iMac for emergency internet access in the hope that I can find out how to fix this. My situation is exacerbated by living in a non-mac friendly country (Portugal), and the only Apple engineer in the whole of the south is about 150 miles away from me making the whole thing a serious pain in the neck. Any help would be greatly appreciated!

[Big Mac]

You've been dumped into Open Firmware because something is seriously amiss on your boot drive. Disk Utility is a very basic (read weak) disk repair tool. Here is what you want: Disk Warrior. Years ago now my iBook became unbootable due to a nasty crash I experienced while booted in OS 9; I thought I would have to wipe the drive, but Disk Warrior repaired the disk, and it has been trouble free ever since.

[allblue]

Oh dear... On my external HD I have Drive 10 (I know that Disk repair is pretty feeble) which has repaired a problem or two for me before, but in this instance I cannot access my ex HD because I can't get the computer up and running in the first place. One thing I forgot to mention above: when I try the mac-boot option in Open Firmware the cd drive (remember I had set the install disk as start up disk in sys prefs) starts to spin up, just when it sounds as though it is about to open up it just stops spinning. I suppose what I am hoping for here is a command I can input into Open Firmware (if that is possible) that gives me some other option because if I can't get past the OF screen I can't do anything.

[Big Mac]

If you need to open the CD tray at the Open Firmware prompt, type eject cd.

[allblue]

Ok, just started up, just a grey screen for about 45 seconds then Open Firmware - eject cd worked ! but I'm not sure if it helps here... Is there a way I can tell it to change start up disk? Then I could boot up the ex HD and start from that to effect repairs...
Unfortunately, I bought Drive 10 online and so do not have a disk with it on...

Appreciate the advice Big Mac (and that's from a vegetarian!)

[Big Mac]

Haha, I am only loosely associated with the sandwich. Glad to provide any assistance I can. I thought you may have had a disk repair CD of some sort but failing that. . . 1) You say you have a bootable external drive. If it's connected, try issuing mac-boot and then holding the option key to see if you can get the boot loader menu. And if that does not work, do you have the system software CDs? If you can't get a hold of Disk Warrior nor boot off that external drive, the next step is to try an archive install of the OS.

[allblue]

Hey I think we are getting somewhere here! I booted the ex HD, held option as recommended and have got a new screen with an icon for iMac (internal drive name) plus what looks like a restart symbol below to the left and an arrow symbol pointing to the right which is very encouraging! Unfortunately, I didn't have a mouse connected to that keyboard, and when I plugged the mouse in it is dead - no red light. this means I can't move the cursor to try the buttons and the keyboard doesn't seem to have any effect. Can I do anything via the keyboard, or should i restart with the mouse attached! That would mean just switching the power off again of course...

[allblue]

Hmm... just read a story <a href="http://www.theregister.co.uk/2005/05/05/apple_mega_patch/">here</a> saying the latest security patch changes the way the system handles tiff files... it was transferring tiffs for a memory stick to my desktop which started this thing off...

[allblue]

Oops sorry! The a-tag doesn't work here!

[allblue]

Lo and behold there was light! I thought I would try switching off, attaching the mouse then switching back on holding down the option key (of course usb needs some system stuff to work I guess) when to my delight, then disappointment, then delight the mouse lit up - but as I looked at the screen even better - it was the apple logo and everything started ok! Just switching to the boot option page (even though i couldn't interact with it) then restarting sorted things. The problem must have been the system trying to boot from the OS install CD which it couldn't do for some reason. I immediately (and rather guiltily!) backed up last week's work, rebooted from the ex HD and am now running volume structure repair. Crisis over!
So many, many thanks Big Mac - you have saved me a geat deal of inconvenience and expense! If you are ever over in the Algarve I'll treat you to a bica (espresso coffee) and madronja (firewater by any other name) which is the traditional regional breakfast! This is what's great about having a mac - not only do you get to use the best computers and software around, the term 'community' really does mean something for mac users as exemplified here.
Incidentally BM, I noticed where you were posting from, and I usually describe the climate here as 'Southern Californian' - 3,000 hours of sunshine a year - just beautiful today - when I realised I had put The Doors on the system...power of association I suppose! This is the end...