title: Access to the remote server is denied because the current security context is not trusted
body: <p>I have a service broker which calls a stores procedure sp_dequeue
  queue -->
      ACTIVATION
      ( STATUS = ON,
      MAX_QUEUE_READERS = 1,
      PROCEDURE_NAME = sp_dequeue,
      EXECUTE AS 'Username'
      );
  In my sp_dequeue i am inserting record in to Linked server...
  So when i am calling sp_dequeue from the magmnt studio it works fine. But when its called automatically via service broker i get this error msg :
  "Access to the remote server is denied because the current security context is not trusted.".</p>
  
  <p>In my linked server property i have checked "Be made using this security constraint" and provided oracle userid and pwd also i have added 'Username' mapping to oracle server.(Both username and pwd of oracle/SQL are different)
  I googled for this error tried mostly all combination.
  Pls do help me in sloving this problem.
  using Sql server 2005 and oracle 10g</p>