Modalless Dialog (with a child CScrollView Window created on Stack ) Crash in OnCancel after calling DestroyWindow

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MFC

Hello Everybody,


I am having a very strange problem with one of my modalless dialog and it crashes.
Actually what i have done is created a modelless dialog as follows:

CDlgVbRecAvail* pDlg = CDlgVbRecAvail::GetDlgInstance();

	if( pDlg->m_hWnd != NULL )
	{
		pDlg->ShowWindow(SW_RESTORE);
		pDlg->SetFocus();
	}
	else
	{
		pDlg->CDialog::Create(CDlgVbRecAvail::IDD, this);
	}
	pDlg->ShowWindow(SW_SHOW);

where CDlgVbRecAvail::GetDlgInstance() is defined as follows:

CDlgVbRecAvail* CDlgVbRecAvail::GetDlgInstance()
{
	if( m_pDlgInst == NULL )
		m_pDlgInst = new CDlgVbRecAvail();
	else
		return m_pDlgInst;
	return m_pDlgInst;
}

and m_pDlgInst is declared in the header file as follows:

static CDlgVbRecAvail* m_pDlgInst;

Now i have one CDialog method OnCancel and is as follows:

void CDlgVbRecAvail::OnCancel()
{
	DestroyWindow();
}

and one Method overriding PostNcDestroy and is as follows

void CDlgVbRecAvail::PostNcDestroy()
{
	delete this;
}

Now the problem arises when I close the dialog it crashes after the call to DestroyWindow in OnCancel method. PostNcDestroy is not being called.

it show the following dialog

http://www.imghack.se/126142[^]

and then breaks in to this class dbgheap.c in the code at line no. 2103

extern "C" _CRTIMP int __cdecl _CrtIsValidHeapPointer(
        const void * pUserData
        )
{
#ifndef WINHEAP
        int i;
        void * base;
#else  /* WINHEAP */
#endif  /* WINHEAP */

        if (!pUserData)
            return FALSE;

        if (!_CrtIsValidPointer(pHdr(pUserData), sizeof(_CrtMemBlockHeader), FALSE))
            return FALSE;


#ifdef WINHEAP

#ifndef _WIN64
        if ( __active_heap == __V6_HEAP )
        {
            PHEADER     pHeader;
            if (pHeader = __sbh_find_block(pHdr(pUserData)))
            {
                return __sbh_verify_block(pHeader, pHdr(pUserData));
            }
            else
                return HeapValidate( _crtheap, 0, pHdr(pUserData) );
        }
#ifdef CRTDLL
        else if ( __active_heap == __V5_HEAP )
        {
            __old_sbh_region_t * preg;
            __old_sbh_page_t *   ppage;
            __old_page_map_t *   pmap;
            if ( (pmap = __old_sbh_find_block( pHdr(pUserData), &preg, &ppage )) !=
                 NULL )
            {
                if ( *pmap )
                    return TRUE;
                else
                    return FALSE;
            }
            else
                return HeapValidate( _crtheap, 0, pHdr(pUserData) );
        }
#endif  /* CRTDLL */
        else    //  __active_heap == _SYSTEM_HEAP
#endif  /* _WIN64 */
        {
            return HeapValidate( _crtheap, 0, pHdr(pUserData) );
        }

#else  /* WINHEAP */

        /*
         * Go through the heap regions and see if the pointer lies within one
         * of the regions of the local heap.
         *
         * Pointers from non-local heaps cannot be handled. For example, a
         * non-local pointer may come from a DLL that has the CRT linked-in.
         *
         */

        for (i = 0; (base = _heap_regions[i]._regbase) != NULL &&
                i < _HEAP_REGIONMAX; i++)
        {
            if (pUserData >= base && pUserData <
                    (void *)(((char *)base)+_heap_regions[i]._currsize))
                return TRUE;
        }

        return FALSE;

#endif  /* WINHEAP */
}

Please help me in getting rid of this crash...
Thank you all.