Cannot Connect to SQL Server Express

I tried to connect to SQL Server 2012 Express through Visual Studio 2012. It was working before until yesterday when it gave this error

Cannot connect to FRANCISPEDS\SQLEXPRESS.
ADDITIONAL INFORMATION: The type initializer for 'System.Data.SqlClient.SqlConnection' threw an exception. (System.Data)

Minutes later, tried to connect again, now it shows this error

Cannot connect to FRANCISPEDS\SQLEXPRESS.
ADDITIONAL INFORMATION:
The type initializer for 'Microsoft.VisualStudio.Data.Tools.SqlEditor.DataModel.SqlConnectionStrategy' threw an exception. (Microsoft.VisualStudio.Data.Tools.SqlEditor)

Index not found. (Exception from HRESULT: 0x80131124) (System.Data)

I have no idea what happened, can someone help? thanks.

Seems there is a problem with .NET 4.5. I think you have to remove non-IFS LSP installed Winsock Catalog Provider. Kindly follow the instructions given on http://support.microsoft.com/kb/2568167.