What version of PSE you are working with ?
Do you have QuickTime installed on your system.? If not then please install and then check
Thanks for your reply.
I am on PSE 11
Yes I have quicktime installed
Select a single .mov file in Organizer, right click it and select 'Update thumbnail'. Please let me know if it brings the thumbnail.
If it does, then search for .mov files, select them all and do as mentioned above.