Messages will not open after upgrading to El Capitan
I upgraded my MacBook Pro to El Capitan earlier today but cannot get Messages to open. After installation of El Capitan, I received an error message when I tried to open Messages "Thee messages database is being upgraded, please wait while it finishes or Quit Messages and relaunch it later." It finished and then the Messages icon just keeps bouncing. I've tried deleting the .plist but it doesn't seem to solve the problem. Please help.
MacBook Pro (13-inch Mid 2012), OS X El Capitan (10.11.2)