I finally had a chance to get back to this and got the file-based spell checker up and going. I thought I'd close the loop on this thread in case others downstream somehow managed to reproduce my silliness.
> I see the n-grams (n=3,4) but the text looks interspersed with spaces. The issue was simply a file-encoding problem: I was (foolishly) editing my dictionary file using WordPad and saving as Unicode, not realizing that this mapped to UTF-16, hence the extra pad characters. Thanks for the tips and the nice work on the spell checker! Ron