Data could not be retrieved from the external data source

Hi,

I am using Excel 2010 - Pivot table to see the data in SSAS 2008. I can create the connection string and the pivot table. The issue arises when

1. I drag some of the calculated measures into pivot table.

2. I try to show the details of hierarchy by click "+" in the pivot table.

In both the cases I get

"Data could not be retrieved from the external data source. Error message returned by the external source. 

An error was encountered in the transport layer."

Any help would be appreciated.

Thanks,

SP

SP