RHEL 4.0 WS unix_chkpwd question

["Blackburn, Marvin" <mblackburn glenraven com>]

Since upgrading to the latest kernel and erratta,
I have been getting the following when logging in to system xxxxx as
user yyyy.
I have seLinux in a monitoring mode.  
What has caused this and what about the password is this checking?

Dec 21 10:35:38 xxxxx unix_chkpwd[17107]: password check failed for user
yyyyy

------------------
Marvin Blackburn
Systems Administrator
Glen Raven
"He's no failure.  He's not dead yet" --William Lloyd George