Hokay so -- I exported a 6 min video in Final Cut Pro 7, with following specs:
QuickTime Movie (via QuickTime Conversion)
It exports beautifully EXCEPT for the first 15 seconds, in which there is a motion file + a title card over it. The audio in that section is also in the export, but it's just a black screen (no motion, no title card) until the first interview cues up at 15 secs. In the Canvas, the entire sequence plays back fine, it's all rendered, and I even use the exact same motion file & type of title card at the end of the video -- so I don't think it's either of files themselves. There are no "in" or "out" markers, and besides, the audio of that section is fine, so it's not shaving off the entire first 15 secs, just the video portion.
I've tried dropping the files into the timeline again, re-rendering, exporting the sequence as it is + nested in another sequence, tried putting "In" and "Out" on either end of the whole sequence, to no avail.
Sounds like a bad H.264 conversion. The problem may be caused by Final Cut just dropping the video frames for the H.264 encoding. This is easy to do with multi-pass H.264 encoding. Try exporting out of Final Cut in ProRes and then encode the H.264 in Compressor.
Brad Wright is software engineer, so it may be difficult to understand what he is saying. He is always happy to explain his greater detail.