This code:

 Set Iexplr = New InternetExplorer
 With Iexplr
   .Visible = False
   .Navigate URL:="http://xyz.com/"
   Do While .Busy: Loop
   ...some more code...
 End With

works in Outlook 2003 (with Windows XP) but not in Outlook 2007 (with
Windows Vista).

In 2003 it opens an invisible instance of Internet Explorer and goes to the
website xyz.com as expected.  Code execution continues normally.

In 2007 the .navigate command opens a 'visible' instance of Internet
Explorer and goes to the website xyz.com.  However, the variable Iexplr
becomes null and any subsequent use (.busy) results in runtime error 462: The
remote server machine does not exist or is unavailable.

Can the code be made to work with both configurations?

Thanks