Mysha has a point and I wish I had thought of it.

If you are using Noteworthy Composer, go to the "View" menu and uncheck "Allow Layering" and see what you get.

If you are importing a MIDI that contains lyrics, Noteworthy puts the lyrics on a separate, hidden single line stave layered under the stave with the notation with notes matched to the duration of the lyric. The grey notes are the hidden notes from the lyric stave. They won't do any harm and shouldn't show in the printout - check print preview to be sure.

If you are wanting a purely instrumental arrangement, it is quite safe to delete the lyric staves.