I had the same problem when I setup a new computer this week. Here's what I had installed:
The problem was that when I was in Photoshop and used the "Save for Web" export screen, the dropdown menu for the different export types (JPG, PNG, GIF, etc) would take an extremely long time to update the preview of the graphic.
After a few days of research , I found that Suitcase was conflicting with Photoshop. Here's how you fix the problem (or at least here's what I did with my situation):
This fixed the problem immediately and now my Photoshop" Save For Web" feature is working really fast. Hope this helps anyone else in the same boat.