Apropos the various comments concerning this issue:

Experience on the RAL farm is that we have seen no trace of this
problem, either in careful updates by hand (using yum) or automagically
(using yum), or the odd system updated using rpm without yum on top. 

The RAL systems are regularly patched so we tend to stay as close to
up-to-date as possible, and we get a nightly mirror from the Fermi ftp
server(s).

Maybe we were lucky... ;-)

Martin.
RAL Tier1/A Systems team