Hmm, Sibelius should not be refusing to load that file - that should be a recoverable error. In the past I thought that Sibelius would load files like that.
Of course we would prefer that Finale not export a MusicXML file with that type of error. This sounds like an error we have seen occasionally before, and it is pretty high on our list of issues to fix. Could you please PM me either here or on the Finale forum with a copy of or link to the original Finale file, or email it to me? Thanks so much!
VP of MusicXML Technologies