[C++] Creare GUI con Win32 API ed errore "Stack corrupted error"

[EmaGuzzetti]

ecco il nuovo codice:

#define STRICT
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <string>
#include <tchar.h>
BOOL CALLBACK unaDlgProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
if(uMsg==WM_CLOSE)
{
EndDialog(hwndDlg, 0);
return TRUE;
}
else if(uMsg==WM_COMMAND)
{
WORD wNotifica = HIWORD(wParam);
WORD wId = LOWORD(wParam);
if(wNotifica == STN_CLICKED && wId == 101)
{
HWND hStat = (HWND)lParam; 
char buff[6]; 
TCHAR * pTesto; 
SendMessage(hStat, WM_GETTEXT, 6, (LPARAM)buff); 
if(buff[0]=='C') pTesto = _T("Salve"); 
else pTesto = _T("Ciao!"); 
MessageBox(0, (LPCWSTR)pTesto, (LPCWSTR)buff, MB_OK);
SendMessage(hStat, WM_SETTEXT, 0, (LPARAM)pTesto); 
return TRUE; 
}
}
return FALSE;
}
int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, LPSTR lpCmdLine, int nCmdShow) {
DialogBoxParam(0,L"MioDialogo",0,unaDlgProc,0); return 0;
} 

i caratteri non gli ho modificati quindi sono unicode...