samba - Apr 2008 - chdir (/root/tmp) failed - but why is it trying?

I'm seeing this in the log.smbd file for v3.0.28a.

[2008/04/14 18:29:16, 0] smbd/service.c:set_current_service(184)
   chdir (/root/tmp) failed

This happens straight after a server startup if I connect to my HOME 
directory (and I'm the only person using the server).  It is noted in 
the log (debug level 1) *before* the entry about me connecting to my home.

There is no mention of /root (or any tmp) in the config file.

I added a line to dump some of the connection_struct info and it seems 
to be a connexion made by nobody (i.e. the guest id).

Does anyone know what is going on here, and what I can do to stop it?