I am facing the same problem,
when creating a metric package always return this error.
I have installed 8.4 version gateway and dispatcher on the same computer
When I press "New Metric Package" from Cognos Connection, every thing go fine
then i create a new data source again everything ok, but when i press the next botton
i get the message "The IBM Cognos gateway is unable to connect to the IBM Cognos BI server" and i need to stop and start the Cognos Service.
did you find the solution ?