@DasDex, good spot. Still not entirely satisfactory though, as it doesn't let the other play see what dialogue options are available, definately more workable though.
On a further positive note, it looks like this problem has been acknowledged, and hopefully some kind of solution will be implemented to resolve it entirely.
It is mentioned in this thread:
http://www.larian.com/forums/ubbthreads.php?ubb=showflat&Number=505707&gonew=1#UNREAD
