Symptoms

Mouse right-click does not work (no context menu is displayed) in Visual Studio 2010.
 

Diagnoses

You can try to perform Repair operation for K2 for Visual Studio 2010 as described in the Troubleshooting section of K2 Designer for Visual studio documentation: Right mouse click stops responding in Visual Studio 2010 for K2 Designer extension.

But in some cases it may not resolve this issue.
 

Resolution

In order to resolve this problem it is necessary to run Visual Studio Command Prompt in elevated mode (right click, choice Run as Administrator) and issue the following command:
 

devenv.exe /resetuserdata

It is also important to close Visual Studio before performing this operation. Note that you have to run Visual Studio Command Prompt in elevated mode even if user you currently logged on as has administrative permissions.