Make sure to include Telerik.Web.UI
in the code-behind of your pages, and not to include Telerik.WebControls. Then make sure all declarated grids are of Telerik.Web.UI.RadGrid type.
Check your references one more time and make sure they point to the newer assemblies.
Also see this
help topic about migration of the grid.
In your references, remove the assembly 'RadTreeView.Net2' as it is not longer used. RadTreeView is defined in Telerik.Web.UI now. See the topic about migration of the RadTreeView
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items