http://screencast.com/t/mZDwbWS8 WORKAROUND: Set the UseCompatibleTextRendering property of RadGridView to false.
In windows 8, Microsoft reduced the length of a string that can be measured/drawn with GDI+ to 32000 characters (from 65535 in prior Windows versions). More on the matter can be found in the following feedback item - https://connect.microsoft.com/VisualStudio/feedback/details/776722/label-control-throws-an-exception-if-its-text-is-set-to-a-very-long-string