This issue occurs because a thread waits for a critical section that is used by another thread in the MFC application. In this scenario, a thread deadlock occurs, and the application stops responding. You run the application on a computer that has Multilingual User Interface (MUI) installed. You develop a Microsoft Foundation Class (MFC) application in Microsoft Visual Studio 2005. FIX: MFC application stops responding when a thread deadlock occurs in Visual Studio 2005 if MUI is installed Symptoms