I've got this problem, too. 
I've recorded a bunch of interviews using Sound Studio -- saved in WAV format -- & am running Mac OSX 10.4 -- the new one -- on a brand new Powerbook G4. I found this other discussion elsewhere in the ES forum: http://nch.invisionzone.com/index.php?showtopic=319 . Has any of this helped you?
I had already tried the select folder suggestion and it didn't work. My audio files were all *still* grey. I also tried the suggestion by the other person there -- to go into the finder, use Control select to get the file & open it using Express Scribe. This resulted in my file name showing up in ES, but it listed the duration as 0:00 and sure enough, it doesn't play.
Has anyone yet come up with any solutions for this? When is ES going to solve these Mac related problems? I can play (at half speed) my files using Quick Time, but I'd prefer to use a software with which I can use a pedal!!! 