editdiary.php is blank if you don't specify an action or forumid (
http://www.blah.net/forum/diarycp/ed...id=x&do=foobar)
That's why there's index.php

.
I tried to fix the URL error that you needed to hardcode by putting $vboptions['bburl'] in the navbit link, but on my installation that made it
http://www.blah.net/forum/http://www...rycp/index.php but I will keep looking for a solution.
Just put a link anywhere on your site to $vboptions[bburl]/diarycp/ and that should work for others to access it.