we have two users here that can't change their passwords.
When they want to, a message that says

"Fehler beim Ändern des Passworts für Server <name of our tree>
Fehlercode: oxfffffda7"

In english it would be something like:
"An error occured while changing the password for server <name of our tree>
Error code: oxfffffda7"

We experienced problems similar to these when the NMAS authentification was
turned on. If you type a wrong password with activated NMAS
authentification on the client (but not on the server) you just get an
error code similar to the one mentioned above, but if you deativate it, it
gives you an understandable message like "Wrong password"
Well I turned off the NMAS authentification on both clients hoping the
error message becomes understandable but it stays the same.
What could be wrong here?

Thanks in advance for all answers.