Thank you for your help. Somehow or other everything spontaneously started to work again. I did quit iMovie but I did not have to shut down my computer. You are correct about the fact that I had just uploaded a bunch of new stuff because I had downloaded the Maverick system. Then I had to upgrade bunches of iWork stuff. That is when the problem started. Next time I will just quit whatever and maybe even shut down to see if everything is resolved without all the detail in your thread. Nan in NJ
As long as everything is working fine, I would leave the files as they are; I would not advise permanent deletion of the files unless you have a backup (maybe through TimeMachine or even an external hard drive). Even as of now, 6 months after my initial response to the thread, these files are still in my Trash. I have not permanently deleted them...just moved them to the Trash. I haven't experienced any problems with iMovie since this solution.
I hope this helps.