Currently Being ModeratedOct 28, 2013 7:00 PM (in response to revyrob)
The hard disk where your library is located may be full or unavailable or permissions may have changed. To avoid losing your work, quit iMovie.
Currently Being ModeratedNov 14, 2013 9:14 AM (in response to revyrob)
Ditto, and this after creating a new project successfully.
Currently Being ModeratedNov 14, 2013 10:04 AM (in response to revyrob)
If it is permissions related, did you upgrade from OS X 10.8 to 10.9 Mavericks prior to the iMovie install? Doing an OS upgrade touches a lot of files all over the hard drive and it might be the case that some files have the wrong owner/permissions. One way to set the permissions to the default across the whole OS is to boot into the Mac Recovery Volume. Restart your Mac and hold down the Command key and the R key (Command-R).
In the dialog box that shows up choose disk utility, then click/highlight your Mac HD in the list of drives listed on the left side of the Disk Utilty Window.
Make sure you have selected the First Aid button on the right side, and then click the button marked Repair Disk Permissions. Disk Utility will rollback all the permissions to a default setting that will eliminate this is a possible reason for iMovie not being able to create a project on your internal hard drive. Otherwise, it may be that you need to free up some extra space even though the hard drive is not completley full,...yet. The files iMovie creates while importing/exporting and final sharing take up a ton of room, so leave your hard drive less than half full if possible (for a 300GB drive, leave 150GB of space open and unused).