Problem with exclude=... in yum.conf

I'm trying to suppress updates to libsmbclient, and have
edited /etc/yum.conf as shown below.  It's not working, as is also shown
below.  The relevant repositories are those for fedora-9 and for
fedora-9-updates architecture x64_64.

Modifying the first exclude line to
        exclude=libsmbclient*-3.2.0-2.17*
doesn't seem to work.

$ more /etc/yum.conf
[main]
cachedir=/var/cache/yum
...
# Till the next version of samba-winbind comes out
exclude=libsmbclient-3.2.0-2.17*
exclude=samba-common-3.2.0-2.17*
...

$ yum check-update
Loaded plugins: refresh-packagekit
Excluding Packages in global exclude list
Finished

libsmbclient.x86_64    3.2.0-2.17.fc9      updates