Hi,
I do have the same problem when I try to compile it with the qtcreator...
So tried using the Qt Command Prompt and the pro executed with out any problem...
But in order to open the .exe genrated I copied the qwt5.dll to the debug folder where the exe was generated...
then it worked well

win32 {
INCLUDEPATH += C:/Qt/qwt-5.2.0/src #your path for qwt source code
LIBS += -L C:/Qt/qwt-5.2.0/lib/ -lqwt5 #your path for qwt lib files.
}
after adding it you need to go to qt Command prompt and
enter
qmake ****.pro
mingw32-make
this will do it but you need to put the QtGui4.dll,QtCore4.dll,QtSvg4.dll and qwt5.dll into the debug folder and then open the executable file...