connect fails to compile: reference to 'connect' is ambiguous

[pospiech]

I get the following error in this line:

void QMicosPolluxController::waitUntilPositionReached()
{
    connect(d->checkPositionThread, SIGNAL(positionReached(bool)), this, SIGNAL(positionReached()));
}

void QMicosPolluxController::waitUntilPositionReached()
{
    connect(d->checkPositionThread, SIGNAL(positionReached(bool)), this, SIGNAL(positionReached()));
}

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The first class is derived from QThread, the second from QWidget.

QMicosPolluxController.cpp: In member function 'virtual void QMicosPolluxController::waitUntilPositionReached() ':
QMicosPolluxController.cpp:1047: error: reference to 'connect' is ambiguous
c:\Qt\SDK\2011.05\Desktop\Qt\4.7.3\mingw\include\Q tCore/qobject.h:313: error: candidates are: bool QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const
c:\Qt\SDK\2011.05\Desktop\Qt\4.7.3\mingw\include\Q tCore/qobject.h:198: error: candidates are: static bool QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
c:\Qt\SDK\2011.05\Desktop\Qt\4.7.3\mingw\include\Q tCore/qobject.h:313: error: bool QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const
c:\Qt\SDK\2011.05\Desktop\Qt\4.7.3\mingw\include\Q tCore/qobject.h:198: error: static bool QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)

Half a year ago, the code compiled with Qt 4.6, now with 4.7.3 it does not. Has anything changed? At least I do not understand the error.