Ok. I think I what is the root cause. I have upgrade qt4 to version 4.4.1 which cause problem with libpng-1.2.37 (which I upgraded from version 1.2.29). I have to downgrade qt4 to version 4.3.2 to successfully compile lyx-1.6.4. Could it be qt4-4.4.1 need to repackage with the new libpng-1.2.37?