I do use the pocket pc version, and ken's technique works. You just need to go to the CustomSlides.txt file and edit manually -- any letter/symbol followed by two tabs produces a "blank" slide that performs no action.
This is so useful that I have defined the [South] slide for all letters/numbers/etc to be this blank "no action", and I've suggested that blank slides (or "no action" slides) might be allowed to be placed through the usual user interface. However, I think manually doing this through editing the custom slides file is actually easier. This is often the best way to customize slides on a large scale, as Marianne pointed out in one post.