I just did a fresh install of centos 5.0 from cd, followed by yum update which installed 399 packages. No failures or errors that I can see.
I have three nics in the box, but am only setting up one at the moment.
The box can ping others in my network, but if I try ssh, telnet, ftp, etc
I see you have Xen on this box, boot into the normal Kernel and see what you get. My guess is it works.
I have 5 boxes, that of which networking doesn't work on 3, always works on 1, and sometimes works on 1. I can install fresh and maybe it works, maybe it doesn't on that one :)
I don't know if it's a Linux Bridge issue or a Xen specific issue. They all work well when not booted with the Xen Kernel.
jlc