Can't boot from my firewire external drive

Question

I have a 80 Gb LaCie firewire drive where I have installed (since Phanter) an operating system. All things were OK until I updated the system to OS X 10.4.10 in my G3 iMac (slot-loading). Since then I was unable to boot from the external drive. I had updated the drive's firmware, installed OS X 10.4.10 in it, but nothing has solved my issue. Can anyone help me with this?
Helder Monteiro
iMac G3 slot-loading   Mac OS X (10.4.10)   iBook G4 - 10.4.10

Answer 1

Helder,
I apologize if I sounded like I was finding fault with your use of English, which I think you use very well. My own abilities with any foreign language are embarrassingly poor ... & I'm not that great with my native English one either!
My concern was that we were not communicating well enough for me to understand your situation well enough to suggest anything that would not make things worse. I'm still not entirely sure of that but let me review what I believe it to be before proceeding:
You have a LaCie external hard drive that both your iMac & PowerBook recognize when either is started up from its internal copy of 10.4.10. With either one, the drive mounts & you can read & write files on the external without problems. The only problem is neither Mac will start up from the external drive, which has a copy of 10.4.10 installed on it in the same way as with your Mac's internal drives, that being booting from the Tiger installer disk, installing the base version of the OS on it & then updating it to 10.4.10 with some succession of Apple updates downloaded from Apple. You have also tried the PPC version of the 10.4.10 combo update. None of this has resolved the problem.
If this is all true & accurate, then I suggest you start by attaching the drive to one or the other Mac while booted normally & seeing if the external drive appears as a choice in System Preferences > Startup Disk. You do not have to select it if appears; the test is just to see if the Mac recognizes it as having a valid OS version. If it does appear in the list, hover the mouse pointer over it until a popup box appears, which will tell you the version of the OS installed.
If it does not appear in the list, it means there is no valid version of the OS installed. If it does, you could try selecting it & restarting, but I suspect from what you have said, it won't work -- the Mac will display a question mark for a while on startup, eventually give up on the drive & start from the internal one. (If so, don't forget to reset the startup disk to the normal one to speed up future restarts.)
Either way, launch Disk Utility & run the "Repair Disk" function on the external drive. If it finds anything wrong, continue to repeat the repair until it passes. If it reports failure, stop & report that here before continuing.
If the drive was recognized in the system preference, also run the "Repair Permissions" step. (if not, it is unlikely this will be an option.) If the drive passes both tests now, try booting from it again by whatever method you prefer.
If it does not work now, I think you will have to reinstall the OS. If you have room on the drive, an Archive & Install will probably work. If not, you will need to consider "cleaner" install methods, which we can discuss if you wish.
Good luck!