It may have been the actual game, as it was only the demo version of Indiana Jones that I was using to test scummvm. When I got home, I copied the files for DOTT to my Zaurus and it works perfectly (including speech!!) Home or m keys bring the save menu, although the way the menu works is a bit dodgy.
In any case, I also discovered that func-shift-m brings up the letter m when you are in the debug window, so that way you can also use the savegame command from the debug window to save your game, quite easily as well.
Thanks!
Carlos