Exporting files from 4.5

Guys I am having a problem trying to export files from 4.5. I select Export .wav or midi and then if I select 'Full Score', and the individual parts I only get the Full Score. All of the individual parts run off, but, they are empty - absolutely no sound, in fact they don't even register (on the slides) during the export. If I try exporting individually it is the same, the Full Score generates, but none of the individual parts produce any sound.

Any tips?