So, recently Nokia released QtSingleApplication under LGPL (found in Qt Solutions). So, I downloaded the .zip file, unzipped it, and copied it to $QTDIR\src\qtsingleapplication. Then, due to some limitations of LGPL, I open Command Prompt, cd'd to that directory, and ran "configure.bat -library", ran qmake, and then make.

In main.cpp I have a QtSingleApplication object instead of QApplication, so I put "#include <QtSingleApplication>" at the top.

So now in Qt Creator, everything seems good - Qt Creator seems to recognize the existence of QtGui/QApplication. But the compiler doesn't:

In file included from c:/Qt/4.5/qt/src/QtSingleApplication/src/QtSingleApplication.cpp:48:
c:/Qt/4.5/qt/src/QtSingleApplication/src/qtsingleapplication.h:48:30: QtGui/QApplication: No such file or directory
In file included from c:/Qt/4.5/qt/src/QtSingleApplication/src/QtSingleApplication.cpp:48:
c:/Qt/4.5/qt/src/QtSingleApplication/src/qtsingleapplication.h:69: error: expected class-name before '{' token

...
And it goes on with errors like that, it basically seems like it can't find the Qt includes, but my environment variables are all good. Any ideas?

~codeslicer