VC++ 6.0 Enterprise edition WindowsXP SP2 A Simple test project was generated with MFC app wizard (dialog based). Code: //////////////////////////////////////////// // The following code was added to CTestDlg.cpp: void CTestDlg::OnOK() { // Start test m_pThread = AfxBeginThread(TestThread, &tinf_OnOkThread); m_hThread = m_pThread->m_hThread; // Save Handle to ThreadFunction //CDialog::OnOK(); } UINT CTestDlg::TestThread(LPVOID lpParam) { int _i; for (_i = 0; _i <= 10000000; _i++) { _i = _i; } // << BREAKPOINT is set here return(0); } //////////////////////////////////////////// // The following code was added to CTestDlg.h: typedef struct STRUCT_TINFTEST { bool bStop; bool bRuns; } struct_tinfTest; public: static UINT TestThread(LPVOID lpParam); protected: struct_tinfTest tinf_OnOkThread; CWinThread *m_pThread; // pointer to thread-function HANDLE m_hThread; // handle to thread-function virtual void OnOK(); After starting the program and pressing the Ok button the thread is started. The execution stops at the BREAKPOINT. Continue with F5 the execution stops again at the BREAKPOINT. Doing this about 300 times (or less if more instructions are in the for loop) Visual Studio hangs for about 30 seconds. In the toolbar "Debug" the commands "Restart" and "Stop Debugging" are enabled as shown when the Breakpoint is reached and the user may continue. The window title shows "test - Microsoft Visual C++ [run]" for the first 15 seconds and "test - Microsoft Visual C++ [break]" for the next 15 seconds. During these times VS doesn't react on anything, even the complete system hangs. A change to another application is not possible (or extremely time intensive). Opening the Task Manager is not possible (or uses too much time). The options are to wait the 30 seconds or using Ctrl-Alt-Del and choose "Logout" (results in a dialog to terminate MSDEV that doesn't react). Is there anyone that knows the problem and a solution? Is it already a problem of VS or a system bug? Thanks for answer Pfister Harald