[G4] External firewire device surprise unmount

[Robert Pearson]

Recently my Quicksilver 2002 (upgraded to 1.4 ghz, 1.5 GB. 10.4.11)  
has started some peculiar behavior. First, the mouse and/or keyboard  
would suddenly not be connected. I use a crappy, cheap USB hub, so  
that's not a problem. I unplug and replug the hub. Problem solved.  
Now, though, my external firewire drive has begun disconnecting for  
no reason I can see. I will hear a click, and then I get an error  
message that a device has been removed without unmounting it. I  
didn't know what was happening until yesterday when I caught the  
drive's icons (I've got it in two partitions, one backs up my system)  
disappearing and then reappearing.

I unmounted the drive, turned it off, unplugged the cable and the  
power cord completely and then carefully re-seated both at both ends.  
Then I turned the device one. A few minutes later, I got another  
unmount error. .

The conjunction of these disturbs me. Have I got a mac that's about  
to die, or could there be another culprit? The firewire drive is  
plugged into one of the mac's own firewire sockets: even though I've  
a Suite Multiport, it and the drive don't get along anymore. I have  
no idea why; their disagreement started eight months ago when I had  
to move the multiport card to another PCI slot to put in a 'deep  
case' fan that fits in a PCI slot when I upgraded the video card to a  
Geforce 6200 to handle the heat. The multiport uses jumper cables to  
hood to the mac's system and I've had to disconnect the firewire one.  
The USB jumper is with all my other devices on a USB 2.0 card I have  
installed.  I have sleep turned off, since my quicksilver didn't do  
well with it before the GeForce card was installed, and now it can  
cause drives to hang, and the monitor absolutely refuses to sleep  
ever since I moved the PCI cards around to install the fan. (Monitor  
sleep worked when I first put the new vidcard on. Go figure.)  
Ordinarily the unmount seems to happen about once a day, and usually  
at night, or when the drives are idle

The drive is currently sitting atop the mac. Could this cause a  
problem? (I hope not, as I've no idea where in hell else I'd put it,  
but I may try moving it anyway.

I have no other firewire device, period. The conjunction of this and  
the USB failure is what I find particularly disturbing. Is this  
coincidence or is something very, very wrong? Is there any sort of  
hardware test that could help me work this out?