The attached file is a Bach fugue midi I found somewhere on the net.
When I import it into nted it shows alright (ignoring sharp flat mixups)
When I import it into musescore the entire bass is replicated into the treble clef.

Asking on the musescore lists I get that the problem is with the midi file http://musescore.org/en/node/15501

I am recommended to use sequencing software to cleanup before importing.
What such software should I try to use?
[I am asking this after wrestling with rosegarden for an hour or so and getting no sound]