"Not enough room in heap zone."

This might help:

https://discussions.apple.com/thread/2623925?start=30&tstart=0

Heap Zone problem

Solution that works for me consistently is to just exit iMovie and relaunch it. Sad I have to do that, but it works. PROBLEM is that by doing this, scrolling credits are sometimes deleted (actually, reverted to an earlier version if they had been edited). Also any titles added will also revert to an earlier version if they've been edited, so be sure to check and be prepared to redo those. (MAYBE it's the editing/changing of a title that triggers the heap zone problem, but that's a wild guess and probably wrong.) Anyway, heap zone error?: Just exit iMovie, relaunch, and check and fix your titles. Then it works, for me, always.

This worked for me

Had a project with a deadline and I ran across this error upon trying to export the movie. Took it into the Apple store and spent nearly 3 hours at the genius bar to no avail. The genius told me there was nothing more he could do and said that I had a corrupt clip. I asked if there was any way to tell which one was corrupt and he basically said no.....

So he sent me away with no answer to my issue and no suggestions. Sorry to say, you've spent over 250 hours on this project but we can't help you.

Thanks.

I then went through and started splitting my project into halves, quarters, sixths, and eighths and published each one looking to see if I could isolate the corrupt clip. Low and behold, every single piece exported to the desktop, and then I imported them all back into one movie (had to spend many more hours getting the transitions and the music to line back up) and then went to export the final project (only 7 mins long) and it worked!

Thanks apple. Someone should do some more research on this heap zone error and let all the geniuses know about it. Looks pretty shoddy when the resident graphic design and iMovie specialist on staff has never heard of the error....

Heap Zone

In addition to the "solution" of exiting iMovie and then retyping all your titles and fixing their timing and placement (which the heap zone error also messes up, sometimes), I found another solution. If you have old events in your Event library, and they contain unused clips, ctl-click the Event, selected "Move Event to Trash", and chose "Delete Unused" from the dialog box. It will not only remove just the unused portion of clips from the old event, but, magic?, you can now render and save your new Project without having to exit iMovie.

The only issues are that 1) Sometimes, it doesn't resolve the heap error, but it usually does, and 2) it sometimes messes up the old Project, so that the old Project looses track of clips in the old Event, even tho they are clearly still in your event library, and Time Machine restoration of the old Event may or may not work, as internal clip numbering may be changed. But if you need to finish your new Project and don't care so much about your archived project, then go for it.

"not enough room in heap zone" error in iMovie

I have the "true" answer to this age old question. It was also confirmed for me by a senior tech advisor at Apple. Here is my case number you can reference to prove it. Case #454595897. There is no fix. iMovie is a 32bit application and OS X is a 64bit operating system. A 32bit application can never use more than 3.4GB of RAM. iMovie tries to pull everything into RAM when rendering. So, if your entire project contains more than 3.4GB of data, it will NOT render the movie. iMovie will also start behaving strange as it gets close to it limit.

You have two options. Split the project in half and render each separately. OR pay $300 for Final Cut Pro which is a 64bit application. Save your money on the RAM. More RAM just lets you have more 32bit applications open at once. Pay more for 64bit applications vs RAM. A lot of people trouble shooting this problem think they solve it by doing special tricks but it is just a coincidence that they may have did something that made the project just small enough to render.

I hope this saves people a lot of time to make up for the time I wasted.

Thanks @dshaffer23. That did save me time. I just broke up my video into two parts and the problem went away.