samba - Oct 2007 - 'Could not peek rid out of sid' error 3.0.25c

Hi,
All of a sudden, my samba logs are filling up with errors like:
Could not peek rid out of sid S-1-5-21-3203556629-3307610231-1688239997-3018

Now it appears that I'm no longer authenticating because I cannot get
to private-by-user directories.

Anyone know how to fix this?

Thanks.

-- James