It is the standard Fedora script "iptables" and it recursively
unloads all referring modules, then the base ones: ip_tables and
ip_conntrack. I can't tell which module it stopped on because
that computer is at home today.
And yes, it really locks up until it's caught by the softlockup
watchdog. Has only happened on a uniprocessor i686 system so far,
but happens every time on shutdown.
Standard Fedora 6 i686 config, updated for 2.6.20, not released yet.
I'll attach it.