Fixing an endless ‘The Messages database is being upgraded’ dialog box

After a rocky day, I rebooted my MacBook Pro last night, and when I went to open Messages, I was greeted with this error message:

Messages is updating…
The Messages database is bring upgraded, please wait while it finishes or Quit Messages and relaunch it later.

Comma splice aside, I let it this sit overnight, with no change this morning. Clearly something had happened to my database, but it didn’t seem like it was going to fix itself. Here’s what I did to get the app going again:

  1. Quit Messages
  2. Kill the IMDPersistenceAgent process via Terminal with killall IMDPersistenceAgent
  3. Searched my user Library > Messages folder for anything with Messages, iMessage, or iChat in the name and deleted it.
  4. Emptied the Trash.
  5. Cleared the preferences cache by running killall cfprefsd in Terminal
  6. Restarted the Mac.

After this, opening Messages brought it to the setup screen. I logged back in with my accounts and am now off to the races. While I don’t like that Messages imploded, at least it was fixable without major surgery.