Everything is going fine now. The problem was that /usr/lib64/qt4/libQtWebKit.so.4 was symlinked to QtWebkit 4.5 library and that was the reason why some symbols could not be found. After correcting the symlink the problem disappeared. However, it seems strange to me, because I have tried and later uninstalled qt 4.5 more than 14 days before and I have not found any other files that belong to qt 4.5 on my system, only /usr/lib64/qt4/libQtWebKit.so.4.5 was there.
Thanks everyone who helped me. Tomas
