When you wish to change from "view all classes" in Speed Grader to a specific class you have to move your curser very fast or the gap between drop downs will cause the specific class selection window to disappear. It can be a little frustrating if you don't move fast. Check out the clip on this post for a quick demo.
Update! It looks like Canvas has patched this problem but you never know if it will rear its head in the future.
