Hello,

Thank you for the provided screenshot. It was helpful for indicating the error you are facing.

We have released a fix for this. Please update the Telerik WinForms VS2012/VS2013 Extensions by following these steps: 
1. In Visual Studio's menu select Tools -> Extensions and Updates...
2. Click on Updates.
3. Update Telerik WinForms VS2012/VS2013 Extensions if update is available.
4. Restart Visual Studio.
I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik

Hello,       

According to the provided brief description, it is not clear enough what is the error that you received after upgrading the Telerik UI for WinForms suite. Could you please provide a stack trace or a screenshot of the error. Thank you in advance.

I would like to ask you to carefully check the references to all Telerik controls in your project and make sure that they are the same version considering the suffix as well (.20 or .40). Better yet, you can remove all references and add them anew by using the DLLs from your fresh installation. Delete the license.licx file. After that, you should rebuild your project, close Visual Studio and open it again to make sure that no references are kept in the memory by Visual Studio.  

I am looking forward to your reply.

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik