Passport Manager Errors

I hope this is the right group...

I am running Windows Server 2003 (64bit enterprise edition).
I have thousands of PassportManager errors (event ID 5006) in my event log:

The description for Event ID ( 5006 ) in Source ( PassportManager ) cannot be found. The local computer may not have the necessary registry information or message DLL files to display messages from a remote computer. You may be able to use the /AUXSOURCE= flag to retrieve this description; see Help and Support for details. The following information is part of the event: 633910877302161092.

We do not use PassportManager, so it looks like all of these are erroneous attempts to log into the server. Does anyone know of a way to block this traffic?

Thanks,

Eric