hi ,
its more like a bug in the last versions of wordpmu...
using the visual editor - make a hyper link with the option "open in new window" (target='_blank') ... is not working!
because the TARGET argument gets removed in the code.
thats because TARGET is not allow as an argument of "A"-tag (see kses.php)
why ? was TARGET removed / or just forgotten ?
i wrote the same thing in my last post (http://mu.wordpress.org/forums/topic.php?id=5833&page&replies=3) .. without comments...