Recently this message started to show up on our windows domain controller in the passsync log file:

...
09/29/11 14:38:50: Ldap error in QueryUsername
1: Operations error
09/29/11 14:39:54: Ldap error in QueryUsername
1: Operations error
09/29/11 14:42:02: Ldap error in QueryUsername
1: Operations error
09/29/11 14:46:18: Ldap error in QueryUsername
1: Operations error
...

Happen fairly sporadically but password changes from this machine are also being abandoned while on others no issues.  This is our only 2008 domain controller as the moment but it was working on this machine and another 2008 DC (that was de-commissioned) previously.

Thanks,
Aaron Hagopian