How to reproduce :

• First I defined my own database as default database.
• Next, I click on the internal database
• Then I click on the default database button
• A window "Default data source modification" appears saying that The default data source has been modified whereas it is in use ... at the same time that the notification of the internet explorer say that :
  "The connection to the server is down but the server may still be running your request."

Then, it is impossible to connect again without restart the server.