The underlying provider failed on Open.

http://th2tran.blogspot.ru/2009/06/underlying-provider-failed-on-open.html

http://msdn.microsoft.com/en-us/library/bb738698.aspx

http://msdn.microsoft.com/en-us/library/bb738698.aspx

http://stackoverflow.com/questions/2475008/the-underlying-provider-failed-on-open

http://social.msdn.microsoft.com/Forums/en-US/2f6d18e2-74b7-4cd8-a596-98c101175bb8/kepp-connection-open-with-entity-framework-5?forum=adodotnetentityframework

http://stackoverflow.com/questions/2113498/sqlexception-from-entity-framework-new-transaction-is-not-allowed-because-ther