Ok, this is weird. SoundBox must just wig out with some specific setting on this type of composed MIDI file. I just recreated your MIDI from scratch in Sonar and saved it as a new MIDI file and Soundbox still won't take it. I opened up other MIDI files I have without any problem at all. That's weird.
EDIT: I added some MIDI reset commands which set settings for the pitch bend sensitivity, pan, and volume and now SoundBox seems to read it no problem. I'll email you the new file.