When you attempt to open Studio and logon to a Foundation site you receive "Object reference not set to an instance of an object" in red text at the bottom of the logon window.
Studio 11, Foundation 11
Object reference errors are generic errors indicating the program terminated because of an unexpected situation in the environment. Known scenarios that can cause this error are:
SQL Server drive space full, causing the database to be unresponsive.
Check the SQL server drives for space issues or other problems that may cause SQL to be unresponsive.