xine debuggin multi threading ...
I have no immediate idea why this would happen, but it is definitely wrong. 
Would it be possible to provide a gdb backtrace of the freeze? If you can run 
xine inside gdb (is that possible in Mac OS X?), just hit Ctrl-C when it 
freezes and type "thread apply all bt" at the gdb prompt. It is best to 
compile a debug version of xine-lib (make clean debug install-debug) to get 
readable backtraces.

