Changing Proxy Authentication Details

Question

Summary
After setting up proxy server authentication and successfully establishing a connection through the proxy server to the WibblyWideWeb, it does not appear to be possible to change the authentication details.
I.e. Removing or changing the Authenticator object (Authenticator.setDefault(...);) appears to have no effect once a 'successful' one has already been used.
Details
I have a GUI application that makes connections to the Internet.
It gives the user the option to configure it to pass through a Proxy server when making these connections.
For this, the user may also optionally provide authentication details for the Proxy server (authentication may not be necessary).
(All pretty standard so far...)
Everytime the application wishes to make a connection to the Internet it first sets up the Authenticator.
If the user has provided authentication details then the following code is executed, otherwise the 'default Authenticator' is set to null:
Authenticator.setDefault(new Authenticator()
     protected PasswordAuthentication getPasswordAuthentication()
          return new PasswordAuthentication(username, password);
});(Again, this is all pretty basic stuff as I understand it...)
With the use of some DBF's ("Developer's Best Friend" - System.out.println("..."); statements) I have been able to detect that once a 'successful' set of authentication details has been retrieved from the Authenticator object, the getPasswordAuthentication() method is never called again.
Therefore, changing the Authenticator with the intention of changing or removing the authentication details has no effect.
One possibility for this happening is because some code deep within the java.net API is caching these authentication details after having detected that they are valid credentials.
Do you have any other ideas?
How can I ensure (without a JVM restart, which appears to be the only current solution) that changes to authentication details take effect?
Thanks for your time.
John

Answer 1

On a Mac, you may need to reset the sync history. As far as I know, not being a Mac user, this is accomplished in iSync. The only other solution that I could think of would be to delete the accounts on the phone, and then sync the phone and see if the new info comes over. However, I believe that resetting the sync history will do it.