Thank you for contacting us.
Looking at the report you sent through the Telerik installer, it seems that the problem you experience is caused by a previous version of the product - RadControls for WinForms Q1 2011. The Windows Installer engine detected that this version is broken and tries to repair it, but can't find its installer.
As a solution, I could suggest you to manually repair or remove the previous version (RadControls for WinForms Q1 2011) and then run the installer again.
Please, let me know if this solved your issue.
the Telerik team