This error message has been seen on AIX if the SYSTEM entry in the default section is incorrect.
An example of the correct configuration for SYSTEM in the /etc/security/user file is:
SYSTEM = "VAS OR compat"
Correct any syntax errors in the /etc/security/user file and try the ssh logon again.
You can run the following command to set this to the default entry required for Authentication services (SYSTEM = "VAS OR compat")
# /opt/quest/bin/vastool configure lam