Finder problem or LaCie HD problem

Question

How do I tell whether my external HD (LaCie d2 quadra) used for TM failed or if the trouble is with my Mac (Finder)?
Today I had trouble saving a pages document. The Finder showed the spinning beach ball When I typed the 1st few letter of the destination folder. I checked Activity Monitor & it showed “Finder not responding.” I force quit the finder & discovered I could not restart since no menu bar. I could not access the application folder & I also did not know any keyboard shortcut to bring up terminal so I could not use
“sudo shutdown -r now” or “sudo shutdown -h now”
I gave up & Manually shut down with the On/Off button.
I probably should NOT have force quit Finder! I should have just restarted.
When I booted up again everything worked OK except the LaCie HD icon was missing from the desktop & the TM would not work (since there was no mounted volume for TM). I repaired permissions, I restarted, I shut off & turned on the LaCie HD --no joy.
I am not certain but, suspect that the Finder problem CAUSED the LaCie/unable to mount problem. I just don’t check constantly to verify that the LaCie volume remains mounted. It may have preceded the Finder problem but if so, not by more than a few hours.
The LaCie HD is connected by FW800. I tried to use FW 400 cable & USB cable & same result. The LaCie power light goes on but I don’t hear the HD noises. I don’t know but suspect that the HD must 1st mount before it makes HD noises.
The LaCie is only 16 months old & under warranty. I hate to send it in especially if it is fine & my Mac is the problem.
Under Disk Utility the LaCie is not shown. Under System Profiler/Firewire it shows up as “Unknown Device.”
Is there a way (log?) to find out When the last TM backup completed? Is there a definitive test to tell if It is the Mac software, The Mac Hardware - (doubtful unless FW 800, 400 & USB ports all failed ) , or the LaCie that is the problem?
Thanks,
Steve

Answer 1

Thanks for the replies.
Pullman,
I looked in Console & did find a backup failed but I had been getting occasional TM backup failed messages for months & usually if I manually backup or just wait , the next one works.
I think that is a TM problem as I checked the forums When it 1st happened.
I did not save the Pages document to LaCie. LaCie is used only for automatic TM backups.
I bought LaCie 11-2007 & used exclusively for TM since. I don’t recall anything about “Mac OS Extended Journaled or GUID partition” but, I followed instructions & it went smoothly & has worked very well so I really doubt I set it up incorrectly.
Thomas, Can you point me to any documentation or even anecdotes about the failure of an external drive causing Finder problems? How can I take your very good suggestion to repair the external (LaCie) disk when Under Disk Utility the LaCie is not shown. Under System Profiler/Firewire it shows up as “Unknown Device.”
When you discuss erasing the drive, you are talking about erasing the External drive, right? But if it is not mounting how can I do anything with it? When you say “If the external disk is connected, turned on and not showing up in Disk Utility, then you've got something more serious going on, probably a hardware failure.” You are referring to a failure of the LaCie hardware not the Mac, right?
Update/ more symptoms:
Keyboard shortcut to switch Spaces stopped working. So did mouse buttons for Expose & Dashboard.. So did Hot corners. Repaired Permissions, no help. Trashed Finder plist, no help. Tried to restart & could not. Had to open Terminal & use “sudo shutdown -r now” & Then it restarted with everything working fine except still no LaCie External TM HD mounting.
Something is wrong with my Mac.  Probably the LaCie is just fine.
I will use disk Utility to Repair disk with Leopard DVD.