Hi Li,
Can you please specify, when does your panel bar get the error? What are you trying to achieve? Please narrow it down to a few steps and tell us what they are, then we will be able to help you.
Generally LargeChange is a property of the scroll bar which specifies how much to scroll when your press somewhere above/left or below/right of the scroll bar thumb.
Greetings,
Victor
the Telerik team
Check out
Telerik Trainer, the state of the art learning tool for Telerik products.