Ubuntu caching config info?

[Tyler Earman]

So I made the bad mistake of trying to change my hostname (just put the
name of the new host in /etc/hostname and rebooted) and it raised 8
kinds of new hell on reboot (custom compiled kernel, used to have KVM
configured).

However I set everything back to the old hostname and it works for a
while but every time on reboot now the network does not allow me to get
packets out.  I play around with the settings a bit and it comes back
online after seemingly random setting changes (dhcp3 config, hosts file,
etc).

Does Ubuntu cache config info anywhere?  I'm frankly at a loss of what
in the heck is going on.  I've rgrep'd the entire filesystem for
references to the erroneous hostname, only to come up nil.

I'm on Ubuntu 9.04 btw

Thanks for your help guys.