When I try to use "Alt-s" (Search) when editing a user book, the editing screen closes and I'm back to the regular SS desktop. All the other hot-keys with "Alt-" work. Interesting enough, I found that "Alt-S" (capital "S") DOES work, while for the other commands a capital or small letter works.
Now I know why -- it's because "Alt-s" (small "s") saves and closes the window when you're done editing.