more DNS problems (F10)

[Tom Horsley]

> nslookup finds the right value, but ping reports unknown host.  I
> haven't changed any of my configuration files.

Sounds like this bug:

https://bugzilla.redhat.com/show_bug.cgi?id=459756

Have you gotten the update for glibc 2.9-3?
(Of course getting updates can take many attempts
if lookups for the names of mirrors keep failing,
but if you try enough, it will eventually work :-).