From my experience I find its always good to call them up after 4-6 weeks if all you see is that the application in progress. When you call them it brings up your application and if they see its been 6 weeks since you filed, they jump right on it to get it done asap. In my case, I called after 6 weeks asking to know the status. The same day they called both by references and issued the License the same day.

A friend of mine also called to know the status, and same thing. references called , License issued.