If you're like me, you participated in the 2015 Safer Internet Day by completing Google's Security Checkup to get an additional 2GB of quota in your Google Drive plan. (If you have not, you can complete the Security Checkup by February 17th to qualify for the storage increase.) Also if you're like me, when Google told you that you had less secure app authentication enabled, you didn't know what you used that needed less-secure authentication, so you turned it off like a good web citizen.
If you've read this far, I'm assuming you've earned the hat trick of "like me", and you also use Google Talk through the OSX Messages app. The next time you tried to log in to Google Talk via Messages after completing the audit, Google Talk rejected your password.
If you want to continue to use Google Talk via Messages, you'll need to re-enable the "less secure" authentication mechanism in your Google account.
- Go to https://www.google.com/settings/security/lesssecureapps
- Select "Turn on"
- Cringe a little bit
- Log into Google Talk via Messages