The observed behavior is the standard one provided by Microsoft for databinding. The underlying data structure (in your case genericDetails.GridDataSource) has its own CurrencyManager which has a Position property. Even if you create two DataTables out of the base data source, the CurrencyManager for the actual data will be one and the same. So when you select a value in the first combo, the CurrencyManager.Position sets the selected value in the second combo. For additional information, please refer to MSDN
The only approach here is to create two distinct data structures containing one and the same data.
I hope this helps. If you have additional questions, feel free to contact me.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.