The data set, DataSet1, is a shared dataset. SQL Server 2008 Reporting Services does not support shared data sets
Hmm, did the upgrade or conversion fail?
It came out you need to update one of the project settings called: TargetServerVersion. To do that right click your SSRS project, select Properties and search for that setting:
The correct value to be set is "Sql Server 2008 R2".