Man, you saved my life!!
I was desperate because my Google Voice stopped working yesterday and I was following this thread anxiously hopping someone could give me a light about how to workaround this issue. Finally I've read your post and thought: it's a too simple solution to doesn't try and it just worked like a charm! Just edit res_xmpp.c and replace SSLv3_method() to SSLv23_method() and recompile asterisk (actually it just recompiled this module). By simply doing this, my Google Voice is now working again!
Where is res/res_xmpp.c located? Could you please provide some newbie friendly directions? I'm stumped.
Found the file and edited it with WinSCP. How do I recomplile it? Still No GV.