[Spacewalk-list] yum not updating needed packages, which are shown on spacewalk

[Will Cladek]

I have a CentOS 5 x86_64 server subscribed to a spacewalk (0.5) channel containing the base and update repo packages for CentOS 5.3 x86_64.  There are 20 packages that need updating, as confirmed by the system information on the spacewalk server.  I'll pick on wireshark here.  Spacewalk shows that I have wireshark-1.0.3-4.el5_2 installed, which is true, and need to update to wireshark-1.0.6-2.el5_3.  However, when I do a "yum check-update" or "yum update" on the system itself, it shows no updates being available.  Furthermore, yum doesn't even seem to be aware that the newer version of wireshark exists:

# yum list wireshark
Loaded plugins: fastestmirror, rhnplugin
Loading mirror speeds from cached hostfile
centos-5-x86_64                                                                                                                                                                                                                                    |  871 B     00:00     
Installed Packages
wireshark.x86_64                                                                                                                  1.0.3-4.el5_2                                                                                                                  installed

Why won't yum show these updates?