If you right click on your Event name (or right-click on one of the clips within the event), does it give you the option to "Optimize Media"? If so, optimizing would probably help this.
If not, open one of your event clips in QuickTIme Player and then click COmmand-I to open the Inspector. Tell us what is listed next to Format:
Also tell us the dimensions of the clip.
The problem is that in the event I have only pictures, no videos. When I insert transition effects between images or insert music not export the video. If I remove all the transitions and music then there is no problem when exporting.
I tried to transfer the project with DropBox to other iMac and it works perfectly and I export the video without problems.
So the problem is in my iMac. Some plist that not erase AppCleaner?
Sorry I have no experience with AppCleaner. If you took it to a Genius Bar, they would probably have you reinstall OSX and then reinstall iMovie, and avoid App Cleaner.
If you wish to try trashing the PLIST, see this tip.