Simple edit of a mpeg4 video in QT Pro.Error incorrect time value

I am trying to do a simple edit of a mpeg4 progressive frame video in QT Pro. I want to cut the last 20 secs off a 3 minute video but I keep getting the

error "incorrect time value". I've tried save, save as, and export to mpeg4 with the settings "pass through". I got this error on 4 different videos, so I don't believe it is a corrupted file. The videos are ones I created myself in Media Composer and then converted to Mpeg4 using Sorenson Squeeze. Also I tried this in "MpegStreamClip" with no success. I could give all the info on the video from "MediaInfo" if that would help.

Does anyone know what the problem may be or suggest another method?