xcode precompiler header
In your xcode proj. You can see a other sources group. there is a xxx_Prefix.PCH. In this *.PCH, If you write the cpp code, you should add  #if defined __cplusplus  #include "MUtils.h"  #endif   Then the precompiler header function would be worked.   Reference: http://www.facebook.com/note.php?note_id=220473491312585  http://forum.soft32.com/mac/Xcode-precompiled-header-files-problem-ftopict47632.html