Howdy MG,
I'm not Mark
and I'll let him deal with bugs and such, but I did just want to add a clarification for others who might be following this discussion.
Changing the _key signature_ does not change the key that the piece is played in, it changes the way the notation is written (sharps, flats). To change the actual key (ie, heard pitches) of the piece, you need to use the "Staff/Transpose actual pitches" command.
I know you know that MG, but some folks who may read your description above may think you couldn't decide what key you wanted the piece in, and were trying to change it via the key signature command.
ttfn,
Sherry