Thanks for writing.
I would ask you to open a ticket and provide more detailed information about the scenario in which you are experiencing the issue, because themes cannot be disabled. If you disable the theme, you will not get the look of the default windows forms controls, as you may expect. We are using our own styling mechanism, so as a result RadControls without themes will look like broken, because the style (colors) and layout settings provided by the theme are missing.
I am looking forward to your response.
the Telerik team
See What's New in RadControls for WinForms in Q3 2010 on Wednesday, November 17, 11am Eastern Time: Register here>>