Qt Learning... Strange error.

[jokerjokerer]

Ok sort of learning Qt. I have a solid experience in C++ just that never used before Qt. I am just at the part that I can also load dynamically at run-time the ui files. With the following code snippet:

QUiLoader uiLoader;
QFile file("sortdialog.ui");
QWidget *sortDialog = uiLoader.load(&file);
sortDialog->show();

QUiLoader uiLoader;
QFile file("sortdialog.ui");
QWidget *sortDialog = uiLoader.load(&file);
sortDialog->show();

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The problem is that I get the error:

: ld returned 1 exit status

Even though as I made all this as a class form the following road works just fine.

SortDialog* b = new SortDialog();
    b->show();

SortDialog* b = new SortDialog();
    b->show();

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What am I missing here ?

PS. I am using Qt Creator 1.1.0 with Qt 4.5.1
And my project file is:

# -------------------------------------------------
# Project created by QtCreator 2009-05-10T10:15:55
# -------------------------------------------------
TARGET = Demo
TEMPLATE = app
SOURCES += main.cpp \
    mainwindow.cpp \
    sortdialog.cpp
HEADERS += mainwindow.h \
    sortdialog.h
FORMS += mainwindow.ui \
    sortdialog.ui
CONFIG += uitools

# -------------------------------------------------
# Project created by QtCreator 2009-05-10T10:15:55
# -------------------------------------------------
TARGET = Demo
TEMPLATE = app
SOURCES += main.cpp \
    mainwindow.cpp \
    sortdialog.cpp
HEADERS += mainwindow.h \
    sortdialog.h
FORMS += mainwindow.ui \
    sortdialog.ui
CONFIG += uitools

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Oh and coding under Windows 7.