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If Motion 5 is quitting unexpectedly, the steps in this article can help with troubleshooting the application. I recommend starting with step 2:
Motion 5: Troubleshooting basics
Thanks, but I'm already on OS X 10.9.1 (was pre-requisite for downloading from the Apps Store), have 8 GB of RAM, have a supported AMD Radeon HD 6490M graphics card with 256 MB of RAM, and 391.66 GB of free disk space. The system should be more than capable of handling the small project I'm working on. Motion 5 is the latest version (5.1), just downloaded from the Apps Store last weekend. Everything else on that list is either already up to date or isn't applicable (not being used). The crashes stopped after I reduced the size of my project file, but now I get to composite separate Motion-created effects in FCPX instead of simply importing one movie clip. I really don't get how a project with only 2000 frames (small, in my opinion) with limited behaviors and filters can so easily bring an alleged sophisticated application so quickly to its knees.