Perhaps an update to the present would be in order.
As mentioned above, synaptic is also broken.
Not everyone can update regularly, especially in locations around the world where broadband is limited and expensive - such as where I live. My last update gobbled up half of my monthly data package.
What version of libxulrunner are you using? Have you tried reinstalling it?
The problem is not Firefox specific. That was only an example. It is ALL gtk apps that return the same error. eg.
synaptic: symbol lookup error: /usr/lib/libgdk-x11-2.0.so.0: undefined symbol: g_source_set_name
gimp: symbol lookup error: /usr/lib/libgdk-x11-2.0.so.0: undefined symbol: g_source_set_name
When running ldd, one finds these apps do not
depend on that specific library, so the error lies in gtk.
libgdk-x11-2.0.so.0 originates from libgtk+-x11-2.0_0-2.22.0-1pclos2010, which yes, I have reinstalled.