External Scratch disk disappears when DV camera plugged in.

Question

Tried searching for this but there are so many things it could be I couldn't find anything that helped....
Hello Everyone,
My Dad's new imac seems to be having trouble accepting his firewire DV camera.
He has an external Lacie hard drive connected to the iMac via FW800. This is his scratch disk for Final Cut Pro.
When he just plugged his DV camera in to the FW400 port of the iMac, the Lacie drive (it's partitioned in to 3) disappeared.
When he unplugged the camera, it re-appeared. We tried plugging the camera in to the spare FW400 port on the back of his external, but this made Final Cut think that the drive was set to "read only" which, doesn't allow Final Cut to operate.
The External drive is partitioned correctly. He's used it fine since he got it.
I am suspecting that it has something to do with the DV camera or the Firewire 400 (6 circuit to 4 circuit) cable. I'm actually away from him at the moment and he doesn't have a second cable to try out but his next door neighbor may do so he's going over to ask tomorrow.
The Camera works fine. The iMac is only a couple of weeks old, if that. It was a reconditioned model so I also suspect there may be an issue with the FW400 port on the mac.
Is there a way to check the integrity of the firewire ports?
Has anyone experienced this problem?
We are trying to eliminate things as we think of them so I will post back any results. Thanks for your time.
Double_ohh7

Answer 1

Studio X,
From your comment on Cartoonguys post I should mention that my Dad's DV camera is a Canon too.
We narrowed things down a bit and it backs up what you've said. With Final Cut closed down, and the DV camera off, the external drive is ok. Turning the DV camera on does not affect anything. Opening FCP does not affect anything. Upon opening the capture window however, the external drive gets ejected and we get finders "Device Removal" warning.
Based on what you told me I searched around a bit and found plenty of comments from people experiencing problems on a single bus. A lot of them seemed to be the DV camera not working alongside FW800.
The next thing we will do is;
1) reset the scratch disk to the Primary Drive and try to capture from the Canon DV camera.
2) try plugging the external drive in to the FW400 port of the mac and then daisy chaining the DV camera through the FW400 port of the external.
3) if that doesn't birth any success then I will try reformatting the drive as a single partition and try it via both FW800 and FW400. (Thank you Gary).
I have a G4 Powerbook and have daisy chained until the cows come home and never had a problem. I have a very fuzzy recollection of trying to capture some of my Dad's skiing footage once and not being able to do it. I couldn't swear on the finer details but this has certainly got me wondering.
Randy,
The "read only" issue confused me as I knew the drive WAS set to "read write". That issue only came up through Final Cut and only when we attached the Canon DV camera. If it happens again whilst we are trying out our options I will open info and check while it is all connected but I think it was caused by a bad relationship.
Studio X, Gary, Randy,
Armed with all your advice we'll play around and see what happens. Thank you very much for taking the time to help and putting us on the right track. We'd be lost without you!
I shall post all results...
Double ohh