Comment 11 for bug 777953

Although the handling of blank custom contact fields is fixed in upcoming 11.10, I have seen this message also with legit authentication issues. In these other less frequent case you should ensure your client is not locked out using https://www.google.com/accounts/DisplayUnlockCaptcha. This happens per client (so other devices continue to work fine) when Google suspects any sort of network issue.

Be sure to post back if this solves your issue as captcha handling should be prioritized upstream IMHO.