I got my aspx site working on my local dev machine.  I have it 
impersonating myself and it works fine.

<identity impersonate="true" userName ="devdomain\myname" 
password="mypass" />

I moved the site to a test domain where the impersonated user is an admin 
on the web server.  Same impersonation just a different domain.

<identity impersonate="true" userName ="test\myname" password="mypass" />

Problem is that no matter what user, valid or invalid, I impersonate in 
the test domain I get this error when I try to browse an aspx page:

Parser Error Message: Could not create Windows user token from the 
credentials specified in the config file. Error from the operating 
system 'A required privilege is not held by the client. '

When I try to repro this on my dev machine by putting in an invalid user 
and I get a different error:

Parser Error Message: Could not create Windows user token from the 
credentials specified in the config file. Error from the operating 
system 'Logon failure: unknown user name or bad password. '

There must be a setting somewhere that is causing this, but where?

Thanks