I noticed you have set the EnableRow/ColumnVirtualization properties to false. Is there a specific reason for disabling the Vitualization mechanism? This will introduce major performance issues, especially on machines with lower system specs.
Furthermore, depending on your version of our controls, you may be experiencing an additional performance hit on tablet pc's, due to the fact that there is a service running that triggers the build of the AutomationTree of RadGridView. You can check if this is the case, by disabling the TabletInputService from TaskManager, and test the performance again after that.
Let me know how it goes.
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