I'm really on WP 3.4.1 but it's not offering that option yet.
First, it would be REALLY nice if you'd put something in the changelog to indicate users have to go through all their default [slideshow] shortcodes and add post_id="#" in order for this to work after the upgrade. I would have done that *before* upgrading if I'd known. (Also, is it really necessary? why change this? it worked so well before and was so easy to explain to non-techie users!)
But okay, even after making that change, it doesn't work. This is what I see - a blank black box: http://www.utexas.edu/ssw/test-slideshow-page/
If you look at the code in Firebug it's loading the unordered list of all the images correctly, just not displaying them. Any ideas on what might be causing this? Thanks so much - and sorry for the rant. :)