If you are connected to a hosted instance of MongoDB, you may experience odd connection drops or timeouts that manifest themselves like this:
After a relatively short period of inactivity, you try to run a query from within MongoChef, but you are presented with a server error message box. If you try again, the query will work properly again.
The reason is that in some configurations, the connection can get dropped by a firewall or a load balancer. This issue is common with MongoDBs hosted on Azure. The folks over at MongoLab have some interesting details on this matter: http://docs.mongolab.com/
After that, your connection should no longer drop.