imap doesn't like my passwd

[James]

I spent days on this problem.
I have dovecot setup to use SSL and IMAP.
I also have a pop account that I had no trouble getting working.
Both use PAM authentication on Linux.
openssl s_client -connect localhost:993
a login test_user test_secure_password
The response I got back was:
a BAD Invalid characters in atom

I changed the password to "abc" and it worked.

The secure password used to work but it was a different architecture 
(x86_64 I think).
The current architecture is armhf.
It may be different versions of the software too.

Dovecot v2.1.7