an error: 'undefined symbol: _ZN7QWidget8qwsEventEP8QWSEvent'

[scosdq]

I have cross-compiled a Qt program and put it on the Raspberry Pi B+.

On my PC platform, the Qt version is 'qt-embedded-linux-opensource-src-4.5.3.tar.gz'. It is installed under directory ' /Qt4_5_3forARM ' on my PC.
So I copied all the files under ' /Qt4_5_3forARM/lib ' to the board with the same directory.

And I added the following two commands into '/etc/profile' on the raspberry-pi board:

export QTDIR=/Qt4_5_3forARM
export LD_LIBRARY_PATH=$QTDIR/lib:$LD_LIBRARY_PATH

export QTDIR=/Qt4_5_3forARM
export LD_LIBRARY_PATH=$QTDIR/lib:$LD_LIBRARY_PATH

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Then

#source /etc/profile

#source /etc/profile

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But when I run the executable file(it has been cross-compiled, and for example, its name is 'Paint') on the board, it has an error: './Paint: symbol lookup error: ./Paint: undefined symbol: _ZN7QWidget8qwsEventEP8QWSEvent'.

So who knows what's the reason and how to solve it ?
Thank you !