I have had CC for a couple months, registered and activated and no longer in Trial mode. I upgraded to Mavericks, and downloaded the 12.0.1. Patch. When I opened AE CC, it gave me the message:
After Effects warning: Could not rename the file '/Users/Chitty/Library/Preferences/Adobe/After Effects/12.0/Workspaces.419.1407351712202401.xml' to 'Workspaces.xml'.
It then failed and quit. I even tried copying the 11.0 Workspaces.xml into the 12.0 folder, which solved that error message, but then it froze and was unable to create "....Preferences.xml" and and whole host of other XML files. It seems to lack permissions to write files into my Library folders, or something like that. I've tried compeltely uninstalling, re-installing, signing out, signing in, and every other imaginable combination of resets to get this to work, and can't. I'm on a 2009 Macbook Pro, and I believe I upgraded straight from Snow Leopard to Mavericks.
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.