Symptoms
When you start SQL Server Management Studio in Microsoft SQL Server 2005, you receive the following error message in a Microsoft .NET Framework dialog box:

Unhandled exception has occurred in a component in your application. If you click Continue, the application will ignore this error and attempt to continue.
Unable to cast object of type‘Microsoft.SqlServer.Management.UI.ConnectionDlg.Personalization’ to type’Microsoft.SqlServer.Management.UI.ConnectionDlg.Personalization’.
Resolution
This problem occurs when you have Microsoft SQL Server 2005 Express Edition or SQL Server 2005 Express Edition with Advanced Services installed side-by-side with one of the following SQL Server 2005 editions:MicrosoftSQL Server 2005 Standard Edition Microsoft SQL Server 2005 Developer Edition Microsoft SQL Server 2005 Enterprise EditionIn this case, the Mru.dat file that is installed by SQL Server 2005 Express Edition or SQL Server 2005 Express Edition with Advanced Services causes this error message.