Heap zone issue?

If you are really lucky, this simple fix may work for you. Turn off (full quit) every other program on your computer. No email, excel, internet, etc and see if the iMovie can process. When I encountered this problem last year, shutting everything else down solved my problem. Unfortunately, that did not solve my problem this year.

I believe the issue is not enough contiguous space but I may be confusing my 'problems'. Hope you get lucky!

switch-off Timemachine while using iMovie ...