I have the same issue after upgrading to Deckling Extreme 6.2 software.
As soon as you fix the audio issue in one of the capture presets e.g Blackmagic NTSC 8bit, they all revert to the correct setting.
However after a restart I noticed that the error had come back. This is a pretty annoying bug.
Oliver
2 x 3 GHz Duel-Core Intel Xeon / 2GB RAM / OS X 10.4.9 / Decklink Extreme V6.2 / FCP Studio 1 / NTSC 8bit SDI