CRM 4.0 upgrade Failed error: An item with the same key has already been added.

Dear All,

 Now i am trying to upgrade CRM Server from CRM 3.0 to CRM 4.0, while upgrading i got the following error:

Action Microsoft.Crm.Setup.Server.ImportDefaultDataAction failed.---> System.Argument Exception: An item with the same keyhas already been added.

Could you please help me to solve this issue

Thanks
Kumar