Hello Phillip Foster,
Thank you for writing.
This behavior is most likely caused by a missing reference to the Telerik.WinControls.UI.Design.dll (most probably, it is missing from your GAC). Could you please make sure that you have this dll referenced? Then restart Visual Studio and all should be fine.
The better approach is to have all the previous version of our suites installed and install only the latest version. This should add the Designer dll in your GAC and you should not experience such issues anymore.
Let me know if you need further assistance.
the Telerik team
Q3’10 SP1 of RadControls for WinForms is available for download
; also available is the Q1'11 Roadmap
for Telerik Windows Forms controls.