[CentOS] samba & samba-common installed then erased, but by whom?

I saw this in Logwatch today for one of my servers:

  --------------------- yum Begin ------------------------


  Packages Installed:
     samba-common.i386 3.0.23c-2.el5.2.0.2
     samba.i386 3.0.23c-2.el5.2.0.2

  Packages Erased:
     samba-common
     samba

  ---------------------- yum End -------------------------

No one, including myself, has even logged into this box in 
the past few days (verified by asking the only other two 
people who have access and also looking at the last & secure 
logs).

And neither /var/log/yum.log or /var/log/rpmpkgs shows samba 
at all being installed/erased/present.

I ran both chkrootkit and rkhunter, and both turned up clean.

Since this box is behind a firewall with only a few IPs 
given access to it, I'm thinking that it's not been rooted, 
but I can't seem to find any other explanation for this.

The only thing that runs on this server is httpd and jetty. 
Everything else is done manually including yum updates. And 
nothing that runs on this machine would ever need samba.

Has anyone ever encountered something like this?

johnn