Bounce to QT Movie only bouncing audio

[dobyboby]

I work for an advertising company and we are bouncing QT's from Pro Tools on a regular basis. Ever since we upgraded to Pro Tools 7.0 with Mbox2, the bouncing process has worked only 50% of the time. When it doesn't work, the resulting bounce creates a .mov file with audio only. I am careful to bounce no longer than the length of the video file, and have tried using both expanded DV format and small QT format, but the bouncing process still remains sketchy. I am mainly bouncing videos of 30 seconds in length, but when I try to bounce a selection less than 5 seconds in length or so, the resulting .mov has just audio in it. This happens pretty much everytime as opposed to just 50% of the time with videos that are 30 seconds in length.

Any help would greatly appreciated!!!

Doby