Greetings Rich,
I am delighted to report that your suggestion does work to allow the import and display of a jpeg which wouldn't previously display! I opened the offending jpeg in Preview, changed the size per the options provided and then imported it into iMovie. It imported as a 1 second image, but using the add freeze frame option, it stretched it out to 4 seconds or whatever length desired. Thank you very much!
There were two other suggestions posted on other threads that I tried. One was to open the image in Quicktime and then import it into iMovie. This also worked and adding freeze frame wasn't necessary.
The other suggestion was to try to use the Ken Burns effect in iMovie, but this wouldn't work for me because the image wouldn't display in the viewing box in iMovie.
My eventual conclusion is that the image as it resided on "photos" on my iPhone was corrupted somehow. The image had been successfully inserted in an email sent to others, but when I copied it into a burn folder on the iMac desktop, and burned it to a CD, it could no longer be imported into iMovie, unless performing your suggestion or using Quicktime.
thank you again,
Joe