Live Capture with a camera via firewire and usb audio interface

Question

I am trying to do a live capture through Final Cut 7.
I want the video feed through the firewire from my HVX200 and the audio feed from a 4 channel usb audio interface (Alesis iO4).
When I have both audio and video input coming in from the HVX200, the live capture works fine.
However, when I change the audio input so that it is coming from the usb audio interface, final cut has an error message saying "Video is not available."
During the preview, I see the video clearly and am getting levels from the iO4.
But when I try to capture, I get the error message.
Is it a processor issue (I've attached my specs below) with problems handling 2 separate inputs?
I'm not quite sure what the problem is.
Any input is greatly appreciated.
Thanks!
Model Name:          MacBook Pro
  Model Identifier:          MacBookPro5,3
  Processor Name:          Intel Core 2 Duo
  Processor Speed:          2.66 GHz
  Number Of Processors:          1
  Total Number Of Cores:          2
  L2 Cache:          3 MB
  Memory:          4 GB
  Bus Speed:          1.07 GHz

Answer 1

Hi MtD,
Yes I am changing the Capture preset to iO4.  Once that happens, it lets me run both the camera and the iO4 into the laptop but then an error message pops up the moment I try to capture it.
I was only trying to use 3 out of the 4 channels of the iO4.
Thanks!