libQt 4.5.1 Undefined symbol _ZTI18QTransformedScreen

I have a dl I am loading that contains the following code:

Code:

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QScreen* qscreen = QScreen::instance();
      QTransformedScreen* screen = dynamic_cast<QTransformedScreen*>( qscreen );

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On loading I get the following error:

Code:

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undefined symbol: _ZTI18QTransformedScreen

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which according to c++ filt is

Code:

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typeinfo for QTransformedScreen

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.

The results of

Code:

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nm libQtGui.so.4.5.1

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contain

Code:

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009a85dc d _ZTI18QTransformedScreen
007da100 r _ZTS18QTransformedScreen
009a8520 d _ZTV18QTransformedScreen

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Anyone have an idea what could cause this problem?