How to solve "Debug Assertion Failled!!!!!!!" error??? in my project,till now i have made some dialogs n all those working properly.....but now in any event,if i wanna display any dialog than its giving assertion failure... error in MFC file.......File F:\rtm\vcTools\vc7libs\ship\atmfc\src\mfc\winocc.cpp file... where actuly this path is not existing in my system........ But when i debug this error than it shows the winocc.cpp file......... there is error in its code.... BOOL CWnd::EnableWindow(BOOL bEnable) { --->error____ ASSERT:IsWindow(m_hWnd)||(m_pCtrlSite!=NULL)); if(m_pCtrlSite==NULL) return ::EnableWindow(m_hWnd,bEnable); else return m_pCtrlSite->EnableWindow(bEnable); } Guide me..how to solve this error????????