Sorry for the late reply – I was traveling. Thanks for the report. This is a known issue, and we seem to have it fixed.
Here is a new version of the v002 Movie Player. This is an experimental build, it has some new code which is an attempt to fix some performance problems which we inadvertently introduced in Beta 4. This also has the fix for 10.7 and 10.8 exception throwing in the QC Editor when stopping the composition or disconnecting the object.
This is marked as Beta 5 – please let us know here how it works for you.