This sounds like a user permissions issue, not a CAS permissions issue, so
increasing your assembly's CAS permissions is unlikely to be of any help.
Are you sure your user account has sufficient permissions for accessing the
registry remotely on the Vista machine?  What happens if you attempt to
connect via regedit?

BTW, adding an assembly-level RequestMinimum for a CAS permission doesn't
cause your assembly to be granted any additional permissions under normal
circumstances.  It just results in your assembly failing to load if it isn't
granted the requested permission.  If your assembly loads after you add a
RequestMinimum, it already had the permission(s) you requested.  (The only
exception to this is if you're also using RequestOptional attributes, which
may have resulted in the implicit rejection of the permission you need.)

Hi,

I have read som article on Vista security stuff and they have drastically
improve system security by giving by default the least priviledge. If you try
to run an action whcih require administration level you will get a nice popup
windows that will informed you that you do nt have the rights to execute such
oiperation and in certain situation you will be able to enter the admin
credential.

That behaviour will affect most all application which was previoulsy runing
with high priviledge.

When you run your applciation under XP or 2000, with which user login were
you executing your applciation ?