MessageBox can not worked in windows 7 embedded X64 OS

Hi, All

I found a problem.
I used MessageBox to display a modal dialog box in MFC program.
When OS is Windows 7 X64 ,both 32 bit MFC and X64 MFC program,MessageBox runs OK.
But in Windows 7 X64 embedded,32 bit MFC program,MessageBox runs OK.
but X64 MFC program can not worked.
Detail is:In Windows 7 X64 embedded,X64 MFC program called MessageBox,returned is right,but “dialog box” can not pop up.

Best Regards
CJ Zhou