>Hi,
>
>Any idea of what would cause the error:
>
>

>Cannot show requested dialog.  
>Additional information: Parameter name: nColIndex. Actual value was -1. (Microsoft.SqlServer.GridControl)
>

>
>The error happens when in SQL Server Management Studio 2008 I right mouse click on Databases and then on Attach.
>
>TIA.

This may help..

http://social.msdn.microsoft.com/forums/en-US/sqltools/thread/ad2b2e0d-aecb-4f95-89a8-04dd27ac4944/