Hi stevek,
Thanks for showing an interest in the problem I was having.
I have tried several things since your suggestion.
Trying to do a "produce" also failed, and that is with the SVRT showing no rendering required.
I will not bore you with what I have done but for the benefit of anyone reading this I will say how I found out what my problem was, I think!
I purchased the Sony 3D camera long before having any means of editing 3D.
As I had taken one holiday video and wanted to use the camera again I loaded all the files, from the first holiday, on to the computer and burned the the files (as data files) on to several ordinary DVD discs.
When I set up the new computer (July) I copied the files from the discs onto a hard drive. I added all the files on to the timeline and did a "burn to disk". It worked.
After editing out the bits I didn't want and did a "burn to disc. It failed. Several times.
Today (17/10/2013) it crossed my mind that the video still stored in the camera would perhaps work better.
I loaded the video from the camera onto the hard drive.
I then loaded the video from the hard drive into Powerdirector 11s timeline. One file failed to load. All the others loaded without any problem.
I ran the SVRT program and it illuminated red in several sections. The majority was showing as green.
I decided to try a "burn to disk", even with the sections that needed rendering.
It worked, though I have still to see what the result plays like.
So after lots and lots of hours I appear to have learnt that
the video as it comes of the camera is perhaps not as good as it should be and any video that has gone through 2 transfers should definitely be viewed with suspicion.