Comment 7 for bug 301601

I had this problem on all my home computers 1pc, 1laptop and 1netbook.
I realized that xinit works ok but executing any gtk programm throws undefined symbol g_malloc_n and something about libgdk-x11-2.....
So googling I found that there was obsolete libraries on /usr/local/lib that shadows good libraries in /usr/lib

    this gives you which: ldd libgdk-x11-2.0.so.0 | grep local

Moving that to another place solved the problem.
I don't know what package caused this problem but I think is repositories bug