[ubuntu-us-mi] hostname lookup bug?

[Robert Citek]

I'm trying to figure out where the issue is with name resolution on
Ubuntu Lucid 10.04.  Here are the symptoms in psuedo-commands:

on Red Hat machine:
$ dig @foo bar
-> 10.1.1.1

on Ubuntu:
$ dig @foo bar
-> 10.1.1.1

Remove bar from DNS on foo.

on Red Hat machine:
$ dig @foo bar
-> no IP

on Ubuntu:
$ dig @foo bar
-> 10.1.1.1

reboot Ubuntu machine.
on Ubuntu:
$ dig @foo bar
-> no IP

Why is Ubuntu still returning an IP for machine foo?  What is being
cleared/stopped by the reboot?

I'll try to setup a self-contained real example a bit later.

Regards,
- Robert