Sudden block of account by gmail.

Out of the blue Google started blocking one of my Gmail accounts on Linux Mint. It's been running fine for months. The rest run fine. It kept giving me this error message. 400. That’s an error. The server cannot process the request because it is malformed. It should not be retried. That’s all we know. I installed that account on my windows box with exactly the same information. I cut and pasted it in fact. It went right through with no problems. It's one of my main accounts and it's dead in the water. I deleted it and tried to reinstall it and I have exactly the same problem. Setup information. Hit continue. "Configuration found" Click done. Goes to "Sign in to continue to Mozilla Thunder bird Email" Put in email address. Click next and I get that error message. Help? Captain Quack.