I am seeing the same thing, although I have a public key so the client starts OK but isn't recognised as the same client by the server. If you take a backup of the state file, you can restore it and it seems to carry on like nothing happened, but it's possible that something is out-of-date.
In my case it is most often the same clients (10.2.0.201), but there are a lot of them, and I believe that it's been happening since we were on 6.3 clients, though I only suspected that the file was being truncated – this is the first time I've seen it.
On a related note. you can set the password using:
without the need for the installer.