MIDI exporting Error

MuseScore version: 1.0
Operating System: Window Vista
When exporting MIDI, the pizz., tremolo did not play in the MIDI but it played perfectly fine during the playback.
Also, the MIDI file messed up the Violin and Harp part so that the part where violin should play was played by the harp instead. So then it sounded like a piece featuring 2 harps.

How to reproduce the error:
1. Create a new score using: Violins 1, Violins 2, Violas, Violoncellos, Contrabasses and Harp, in that respective order.
2. Input notes for both Harp and Violins 1, few Tremolo notes for Violins 2, and few pizz. notes for Violas, Cellos, and Contrabasses
3. Use the playback button. Listen to the sound, make sure tremolo and pizz are play.
4. export the file in MIDI format.
5. Play the file and the Violins 1 and Harp part should be mix up so that 2 Harps are play instead of Violins 1 and Harp. Tremolo and Pizzicato notes should also did not play in this MIDI file.

Bug: MIDI exporting Failure since the musical instruments parts are all mess up.
Request help: Please help me find a solution to this problem. I need to have the MIDI File a few days from now. It's for a project.