QT4.6.3 to QT4.7.3 Font problem (Chinese)

[batileon]

I am having a simple QT4.6.3 program which may change language (toggle english<==> chinese)

QFont f = QFont( "Luxi Sans", 11 );
    try
    {
        qApp->setFont( f );
        app.setFont(f);
    }
    catch(exception e)
    {
        Logger logger;
        logger.error("main.cpp","main()","qApp - set Font: Unknown exception" );
    }

QFont f = QFont( "Luxi Sans", 11 );
    try
    {
        qApp->setFont( f );
        app.setFont(f);
    }
    catch(exception e)
    {
        Logger logger;
        logger.error("main.cpp","main()","qApp - set Font: Unknown exception" );
    }

To copy to clipboard, switch view to plain text mode 

No exception was caught in the log.

After porting to QT4.7.3, I found that the Chinese font changed, like bold or set to a bigger size. I would like to know if there's any change between QT4.6 and 4.7 that leads to this problem?And, how should I correct this? I've tried setting a smaller font size and it's not working.

Thanks!