How do I resolve share frame errors (-1) with frames in which FCP seems to place a transition mark in the form of an L-shaped or reverse L-shaped figure?

Question

When I try to use Share to a master file, I get an error that states:  "The share operation Master File has failed.  The operation could not be completed because an error occurred when creating frame 158 (error -1)."  This has occurred with different frame numbers.  When I delete them, it might disappear for that frame, but then shows up later for others.  It seems that the problem is occuring right at the transition point between two clips.  FCP seems to be putting an L-shaped figure on the last frame of one clip and a reverse L-shaped figure on the first frame of the next clip.  The faulty frame seems to be one of those two frames.  The clips I am having trouble with were from an old, non-digital cameral.  We had converted them to DVDs and then I converted them to MPEG-4 files using Mac X DVD Ripper Pro.  The converter seems to work fine and I can play the converted movie with Quick Time.  Also, FCP will import the converted movie and works just fine with it as a clip and in the timeline.  But when I try to share, I keep getting these errors.  Short of deleting all of these old clips from the movie, which would be sad, how do I solve this problem? 
After looking at previous discusion threads I have already saved to a new project, deleted the clip and re-imported it, and eliminated the transition effect from between the clips.  But I still get the same errors.
I also get an error when I try to share to DVD, but that error is a "0" error that doesn't mark the location of the problem.  I'm assuming it is the same problem as the one when I try to share to master file.
One other weird thing is that in a slightly older version of the movie with the same clips, I was not able to share to DVD but it did share to a master file.  That almost seems like pure luck right now.
Please help!

Answer 1

MPEG-4 should not be used in FCP unless it is converted first or optimized in the application.
Trash your preferences. Trash your project render files. Switch off background rendering. Do not re-render. Export your projects.
Ignore the last frame and first frame indicators.