I use CS3 and I have no problem clicking on the video section and changing the export frame size to 320X240 and changing the pixels aspect ratio to 1.0 so I am not sure what the issue is.
It would be nice to be able to export to JPG but creating an action in Photoshop will allow you to change an entire folder of BMPs to JPG with one fell swoop.
Steven
http://www.stevengotz.com