[CentOS] IPv6 on Centos 6

An update to close: it's a vmware issue:

* new centos 5 creations exhibit the same behavior
* a few months ago, we migrated from an esx 4.0 cluster to a new esx 4.1
cluster
* we've just recently started using a new centos 6 template; the centos
6 system that's working was created before the migration
* a fresh install on esxi 4.0.0 worked fine; when the vm was restarted
on the new cluster, it exhibited the same failure.  I'm hoping to get an
esx 4.0 instance running to I can try the same test, as it seems that
esx 4.0 vms will migrate properly and work.  Failing that, we can clone
the working centos 6 system for now until we can work with vmware to
figure out what's going on...