The other day my Google Apps account randomly stopped working in my Mac Mail application. The ‘the password you entered is invalid’ error kept popping up, even though I knew it was correct. After some digging, I found that occasionally a Google Apps account might become locked for one reason or another. Unfortunately the problem and the fix wasn’t obvious, but I eventually found a solution.
To unlock your Google Apps account, go to: https://www.google.com/accounts/UnlockCaptcha?, fill out the Captcha, and your account should unlock.
Feel free to leave comments or possible reasons for why a Google Apps account might get locked.