Have you by any chance set a password policy in the directory manager app?

Can you also just verify connections work without user/pass authentication by commenting out the auth-user-pass line in the ovpn file and also the "plugin /usr/lib64/openvpn/plugin/lib/openvpn-auth-pam.so openvpn" line in /etc/clients.conf, then restart OpenVPN? You should find you can get a connection without being prompted for a user/pass.