PAM failure with proftpd yet session runs fine?

[KraGorn]

Can someone suggest what's going on here ... from my syslog:

May 2 20:27:26 www proftpd[15571]: 10.0.0.2 ([10.0.0.3]) - FTP session opened.
May 2 20:27:31 www proftpd[15571]: 10.0.0.2 ([10.0.0.3]) - PAM(myuser): Authentication failure.
May 2 20:27:34 www proftpd[15571]: 10.0.0.2 ([10.0.0.3]) - FTP session closed.

This happens with every successful FTP session, in spite of the second log entry the user logs in and transfers files fine ... also, trying to log in with an invalid username/password is correctly bounced.

The users can also log in using ssh, so for all intents and purposes things *appear* to run without a hitch except for this log.
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