iMovie Export Error

I have a project that is 3 and a half minute project and I'm trying to export it and when i do it gets to about 7 minutes remaining than it gives me an error message saying

The project could not be prepared for publishing because an error occurred. (Not enough room in heap zone / )

And when i try to share to youtube on it it won't work

What can i do to fix this problem

You would probably be better served in the Movies and Video forum here...