[CentOS] xulrunner 1.9.0.19-1: Does it exist or what?

According to 'yum info xulrunner' version 1.9.0.19, release 1.el5_5 exists and is an available package. But when I try to update it, yum claims there is nothing to do and when I try a general update, yum complains that it cannot update firefox because it cannot find xulrunner

= 1.9.0.19-1. What is going on here?

I am doing this on a desktop x86_64 system that I recently brought up to CentOS 5.5, using the DVD ISO I downloaded to my laptop. I'd like to finish this update, but I am having this strange problem. I am getting the same problem on my (i686) laptop. I'm guessing that the updates repos are presently broken?