I am sorry to hear that you have encountered troubles with the Toolbox integration of the RadControls.
We have encountered an issue when you have the latest version of RadControls for WinForms (Q1 2012 or newer) and an older version on the same machine. In this case some controls are missing from the Toolbox. If you have older version of the RadControls for WinForms I suggest you to remove them if it doesn't interfere your work. I want to let you know that we have implemented change that will resolve the issue and prevent it from happening in future.
You can try to resolve the duplicated Toolbox items by resetting the Toolbox (right-click the Toolbox and select 'Reset Toolbox').
I hope this helps.
the Telerik team