When I transfer from my Sony DCR-DVD108 into IMovie w/USB the clip sequence is out of order from when I shot it. Random clips and no longer in sequence.
To quote from http://support.apple.com/kb/HT1096: DVD camcorders require that you "finalize" the DVD disk before importing content into iMovie (unless the "finalize" function is not offered). Refer to the documentation that came with your DVD camcorder for details.