Hello,

Maybe you haven't edit your .pro ??

Qt Code:
  1. INCLUDEPATH += . ; C:\Qt\2010.02.1\qt\qwt-5.2.1\src
  2.  
  3. LIBS += -LC:\Qt\2010.02.1\qt\qwt-5.2.1\lib\qwt5.lib -lqwt5
  4.  
  5. DEFINES += QWT_DLL
To copy to clipboard, switch view to plain text mode 

Try that and change it to the right values !!!