After Effects 12.1 crashes on start up

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.

Any suggestions?