mythtv and retune

Since the au retune I haven't been able to get mythtv to tune to channels 9 or 10 on boot. If I shut down mythtv and manually run a w_scan then restart mythtv it works (without touching anything in mythtv), so I'm guessing my card is failing to automatically detect one of the various dvb-t parameters that must have changed, but w_scan is figuring it out... Does anyone know exactly what the retune changed? All the frequencies appear to be the same... Thanks James