When open an existing report, BIDS only showed a long line of codes, no actual report layout at all

 

 

It seems that the error message you have provided is a known issue in SQL Server 2008. The issue has been fixed in the latest SQL Server 2008 R2 build.

To solve the issue, please try to remove the code parts: DataType=”Integer” in your xml file, and you can follow

 

Thread: http://social.msdn.microsoft.com/Forums/en/sqlreportingservices/thread/23cb9754-be0e-435c-b2ee-820eb84646c5