hi,
I think I found the answer:
iMovie does not work with muxed MPEG-1 and MPEG-2 clips
When using any version of iMovie, please note that you cannot import muxed (multiplexed) MPEG-1 or MPEG-2 video clips into projects. If you try, one or more of the following things can happen:
* iMovie refuses to import the clip and displays an alert instead (such as "File could not be imported because QuickTime could not parse it. -2048").
* iMovie allows you to import the clip, however:
o You won't hear audio on playback.
o You won't see video on playback.
o When you export the project to QuickTime, iDVD, or a connected camera, the clip no longer contains audio.
When files are muxed, they contain interleaved audio and video tracks (they're mixed together instead of stored in separate tracks). Because of this, iMovie cannot support them.
If you want to find out if a movie file is "muxed," follow these steps:
1. Open the original movie file in QuickTime Player.
2. From the Window menu, chose Show Movie Info.
3. Click the More Info disclosure triangle in the Movie Info window (if it's closed).
4. Note the entry next to "Format."
If the format is "MPEG1 Muxed" or "MPEG2 Muxed," you can't use the clip in iMovie. You may want to consider using a third-party utility to convert the clip to DV format for use in your iMovie project.
Note: If you have the QuickTime MPEG-2 playback component installed, it may not change the issues described above. Editing muxed MPEG-1 and MPEG-2 files is not supported in iMovie, even with this component installed.
Regards