Could not load file or assembly Microsoft.Crm.Sdk or one of its dependencies:- MS CRM 2011

Hi,

We migrated our project CRM 4.0 to CRM 2011, While I was trying to update the plug-in from plug-in registration tool. I am getting the

below error.

System.IO.FileNotfoundException : Could not load file or assembly Microsoft.Crm.Sdk or one of its dependencies

Any help greatly appriciated..

Thanks,

Srikath Reddy