found this in a search from Marianna over at Avid.
1. The error is related to a file access problem. Look up the files or folders you try to access with the Apple Finder (eg. your mediafolder). Select the folder and go to File - Get info - Permissions. Change the permissions to Read&Write.
2. You may see this behavior on some versions of the Mac operating system if you have the "fast user switching" option enabled. If you get this error, disable this feature.
3. This can be caused by a conflict with newer AIR plug-ins. It is fixed in Media Composer 18.104.22.168 but if you did not remove ALL remnants of MC then MC 6 will also fail.
Please try the following:
- Go to Macintosh HD>Library>Application Support>Digidesign>Plug-Ins
- Move (or delete) the plugin files that begin with "AIR" (there should be 20 of them)