Failure: Couldn't find mech GSS-SPNEGO

About every minute or so I'm getting a pair of entries in LDAP log for...

"SASL Failure: Couldn't find mech GSS-SPNEGO"

The server is a Open Directory master and has File Sharing and VPN services running - and nothing else.

I could not find anything that mentions the error online.

But I did find this KB...

http://support.apple.com/kb/TS3861

I thought I'd just turn off GSSAPI authentication by following instructions on that KB, but the errors still continue.

So obviously there's some sort of a web service that's trying to authenticate to Kerberos via GSSAPI.

But I cannot tell the source.

Any ideas?