Do you have a sequence selected in the project panel?
Select a clip in the sequence. (Or right click on it.)
I had a similar problem myself today, My 'Edit in Audition' was greyed out.
My problem is the .sesx (Audition Project files) are not associated with Audition within Windows.
Find or make an Audition .sesx file (I found one in "My Documents\Adobe\Audition\6.0\")
and make sure that file extention is assoicated with (or opens with...) Audition.
Not if I Right-Click a clip, the 'Edit with..' is available.
i can see on right click edit in audtion however it doesnt open in audition and renders and replaces clips.
even with audition open it doesnt open audio from within premiere. something has gone horridly wrong