Group Policies and Vista - can't reset value

Greetings All,

I have been noticing a problem with our Vista machine and the ability to
remove settings configured through GP in a Server 2003 environment.

It seems once we use a GP to enforce a settings change, if we then set the
enforced setting back to "Not Configured" the setting doesn't clear. If we
choose disable, instead of "Not Configured" that will work. This is a major
problem.

Here is an example:

I work for a school district, and at the beginning of the school year, we
place all the students in an OU that has a GP called no_internet associated
with it. This GP points the students IE browser to a bogus proxy that won't
allow connection to the Internet. Once the student returns a signed AUP, we
move their accounts out of that container and into one that runs a GP that
has no configured proxy settings.

All XP machines return to autoconfig of the proxy settings and can connect
to the Internet without issue. However the Vista machines continue to try to
connect through the bogus proxy, even though the GP no longer points them
there. Is there a way to stop this behavior and revert to processinfg GPs in
the same manner that XP does?

All policies have been created from a Vista workstation.

Any thoughts?