/usr/include/qt4/QtCore/qtconcurrentfilter.h:227: error: expected nested-name-specifier before numeric constant and other errors compiling Qt4

If you see a load of compile errors from Qt4 classes when doing a compile, this is sometimes caused by your #include statements.
To fix it, replace all the #include <qwhatever>with a single

#include <QtGui>

instead. (For GUI elements anyway. See /usr/include/qt4/Qt directory for other default includes like QtNetwork etc etc)
You should be using that anyway, but QT3 habits die hard.