Canon mini Disk camera doesn't work if external drive connected

Question

A long story.      Anyway, I have a MacPro Intel Dual Core 266 Ghz with 5 Gbs RAM,  4 internal hard drives HD1~HD4 (HD1 OSX 250 and three 500Gb) and two external HD5 (two partitions~HD5 & Time Machine Backups) and HD6 (1 Tb each).
I've been using a Canon mini DV video camera FV-M10 (Firewire 400) for live video (Skype/iChat) and also for importing video into Final Cut Express, After Effects or iMovie up until a few days ago.  Both "live" video and from the recorded mini cassette tape.  Then all of a sudden not one of the software recognized my camera anymore.  I tried both Firewire 800/400 and USB2 connections using a few different cables. In Skype...(sometimes) it automatically shows the name FV-M10 in the camera slot, but the screen is black.  No, I checked if I left the cover on.  I checked my Sony WX-5 digital camera and see if that is recognized.  Yes, both pics and AVCHD videos are seen using the USB connection. 
The problem started like this.
I was downloading a file.  Had to work for an hour and when I came back upstairs.  I noticed that the screen was frozen.   So, I shut the Mac down.  And when I started it again, well nothing happened except for a grey screen.  A half~sized cursor was stuck up in the top left.  But, my mouse also had a cursor which was movable.  
It wouldn't even recognize the OSX Install Disk holding down "C" or "Option".  Only starting with "Shift" held down, "Safe Boot"  could I use the basics like Mail, Safari, Firefox.   NO sound and no video. Tried a few times as well as cleaned my OSX HD1 hard drive and re-installed from "Safe Boot" mode".   So, I had it sent into Apple Tokyo for repairs.   Apple put in a new board.     Great!      I came it back in two days.   I cleaned the OSX hard drive and re-installed Mac OSX with the up-dates as well and got some of my main backed up stuff Mail, bookmarks, address book etc.   It started fine.     But, when I went to use Skype, iChat, iMovie or Final Cut Express  they still couldn't recognize my camera.  I had been using the Canon FV M10 camera for a few years with both external hard drives on.  There were never any problems until just before I sent it into the shop.
There was only one way to use my camera.  Un-Plug the external HD6.  Then the camera functions fine.  but remember I had been using this camera with both HD's for around two years without any problems.
Notes on symptoms:  and what actions I took.  
Front connections: FW400 Canon camera.  FW800 (Tried connecting HD6)  
Rear Connections: USB2 1) MidiMan 2 x2   2) mouse  3) Canon Printer
                               FW400 HD5  FW800 (tried HD6)
With HD6 Connected.
iMovie 11 9.02 : Start iMovie  O.K.  No camera on.   Turned camera "on" then "No Camera Connected" notice came up.   (did this a few times)   Turned camera off.   Quit iMovie. 
2nd start:  Camera On.   iMovie freezes.   Spinning Colored beach ball.   I then Force Quit Option-Apple-ESC
iMovie shows (not responding)  When I turn off the camera.  (not responding) disappears and iMovie is working again.  But, "No Camera Connected" shows again.  Quit!
Un-Plugged (Ejected) HD6.
When I un-plugged HD6,    (tried both the front and rear connections).   iMovie still on.  
"No Camera Connected"  I Quit iMovie.
Re-start iMovie:  Camera on… Live video and record miniDV tape can both be seen. 
Skype:  Both live video and mini DV tape recording even plays back over Skype screen.
iChat (same as Skype) O.K.
Since Apple replaced the board 661-3932 Card Video, NVIDIA GeForce 7300 GT which cost just about $X00.00  (¥XX,000).   I assume that they don't also check all the connections etc. I mean from the connector to the video board.
The call to Apple Tokyo today.  
Just talked to Apple (Mac) Tokyo about my computer problem.  Seems like they're trying to squeeze their way of more repairs by saying I have a hard drive configuration problem.   But it doesn't seem like that!   I worked with it 2~3 hours today...and  here is the basic problem.
I've used the Canon FV M10 mini DV camera with Skype, iChat, iMovie and FCEx for few  years  (HD6) is over a year old-the most recent add on) with no problem.    With both external 1Tb hard drives.  And Apple said that it's a 3-party problem.  (different makers etc.)  But, it's NOT!     Yes, they put in a new board.   But, I'd say the problem is from the connection (where I plug the cable into the Mac)  to the board. 
When I connect HD6 (1Tb ext hard drive).   FW 800 (either back or front connection) the video camera doesn't work in  Skype, iChat, iMovie, or Final Cut Express.     If I eject and Un-Plug HD6  all of them work fine.  The camera "live" or the camera playing back the mini DV tape video.
Wouldn't this be a problem between the connections (front & back) to the new video board?  Or does anyone have an answer.   Apple seems to have said, "We can't help you".   Please someone help!  thanks

Answer 1

+My mini isn't responding to startup commands like "C" or "D" from the keyboard.+
You'll need a wired usb keyboard for these commands to work -- and the Apple Aluminum keyboard won't work either.
But just about any PC usb keyboard will work. Alt maps to Option and Win-key to CMD.