I just installed the 12.1 update of After Effects, and now I can't open the program. When I try to start up AE, I get the error message:
After Effects warning: Could not rename the file '/Users/USERNAME/Library/Preferences/Adobe/After Effects/12.1/Workspaces. 773.1407350999826081.xml' to 'workspaces.xml'.
I just tried uninstalling and reinstalling AE. Same problem.
Mac OS has incorrectly set the permissions for some files.
When you upgrade a Mac OS (as opposed to installing the new version fresh), Mac OS will _often_ set permissions of folders and files incorrectly.
You'll see this problem in programs like After Effects in the form of error messages saying that a file can't be written, overwritten, or renamed.
To fix this in the case of After Effects, go to the preferences folder and set the _entire_ preferences folder ( /Library/Preferences/Adobe/After Effects/12.0/ ) and all of its contents to be writable, not read-only.