Suddenly, After Effects can't find preferences

Hello, I recently upgraded to After Effects CC 2017 and when I tried to launch it for the first time, I got the message

<After Effects can’t continue. Error while accessing the preference files inside “/Users/williamneff/Library/Preferences/Adobe/After Effects/14.0”, please verify the file permissions and try again.>

I uninstalled CC 2017 and reinstalled the CC 2015 version, which I've been using, but now I get the same message. The folder and preference file the app's looking for don't exist. I've never had this problem before. I'm running OSX 10.10.5 Yosemite and I'm hesitant to upgrade because I'm in the middle of a big project (now on hold until I can get After Effects back). Does anyone know what's going on?

Wm Neff