Hi Kirk
The beta version did nothing to solve this issue and I have reverted back to the original version.
I have checked all file extensions.  Oddly, some Jpegs were names cr2.
When I open PM many images cannot be rendered.  The number and files change after each opening of PM - it is not consistent.
If I move to the larger preview window, I cannot see the files in large view, however, I can see the thumbnails.  Then, when I move back to thumbnail view page many of the previously unviewable images can be viewed.
None of this is consistent other than:
1.  Many images cannot be viewed in thumbnail view
2:  When you move to the larger view window, the thumbnails at the page bottom are viewable.
3:  Upon going back to thumbnail view, many but not all the images are viewable
4:  Metadata can be read on some images, but not all.
All images and metadata can be viewed in Bridge.
I have no idea as the problem is not consistent with files.  Iain