The last couple of times I tried to close a M100 project I got a notice saying something like, "Close command could not be executed. File not found." I had to force quit. This happened with two different projects. One of them was brand new with just one bin. Anybody have any idea what's going on?
This is a known bug that Media 100 has never bothered to fix.
It usually happens if Media 100 has been open overnight (but still rarely... so that alone won't cause it). My guess is that some Mac cron tasks run and/or permissions change and then M100 is unable to save.
The only thing you can do is force quite out... I believe someone also suggested that you can save to an external firewire drive (or maybe a different volume) so you can at least make sure you have your most recent save point.
Do a search in this forum and you'll find a couple other posts about this.