Thanks, Hunter. Yes, I have the right Open G notes and tuned down as appropriate, i.e. low E tuned down to D, etc. The tuner would say that it was now a D, same with the other notes that I had to change. Then when I'd strum all the open chords, it sounded bad. I'd then get on this site using the tuning section to retune the strings by ear, and I'd get it right this way.

To try to solve the mystery, next time I'll take some more specific notes about which strings ended up out of tune and by how much.