I have had a look through several relevant threads, but am not getting a solution from them.

Background. (Bit of a shaggy dog story, sorry)

In the UK, I set up an HP PC to run a Hauppage DVB-T USB for Freeview in MediaCentre on Windows 7.
Came to NZ last year, lived in the caravan at Hamilton Park, and got a freeview arial rigged up to a cabbage tree so we could watch TV in the caravan - usb dvb-t worked fine.
Moved caravan to a gorge near Waihi, and couldn't get TV signal, so bought an AverMedia USB DVB-S and DickSmith Satellite Dish bolted onto the caravan. Bit of fiddling, but got it working OK with aid of a signal meter - had to go for USB because PC is low-profile and only takes half-height PCI cards.
Then we moved into a place in the sticks outside Hamilton, got AverMedia DVB-S working fine through the dish on the house, all using the same settings as for our one - 11300 frequency (Hauppage DVB-T also worked fine via freeview arial on roof).
Moved again to house in Hamilton, which had a satellite dish already, but only an old terrestrial TV arial - so DVB-T was out of question. With a lot of fiddling, I got the satellite dish working via the Avermedia DVB-S, main issue seemed to be the frequency was different, which I think was 10750 instead of 11300.
This worked fine for about a month.
Today, Genesis came round to change our electricity meter. So, I switched off the TV, PC, and other bits of equipment like that. I didn't unplug the Avermedia box. This evening, I powered up the PC & TV, etc., but couldn't get any channels. That often happens when the PC is rebooted, and what I usually do is power off the AverMedia box, unplug the USB, power the box back up again, and plug the USB back in - and then it works.
Not tonight. I took a look at the Avermedia application - it was empty, no settings, no programs. MediaCentre still had the programs, but could not get a signal. I went through MediaCentre setup again, could not get anything. As far as I can tell, the AverMedia box is working, but hard to tell when the only indication of life on it is when it is actively picking up a channel.
I tried changing the frequency to 11300, just in case, but no luck. I am pretty sure it was the old default for sky dishes at 10750 - but I set it up when I had just arrived back from a one-day two-leg flight from the UK, so was pretty spaced out when I did it, and didn't make a note of the settings (duh!).
I do recall it was a pain trying to get a signal before - and when I did manage to get it working, I kind of walked a way from it with my fingers crossed, hoping it would just keep going.
I don't really get how my settings would all get lost like when the power to the house was switched off - we had a couple of power outages while this was all working, and it wasn't a problem.
I hooked up the signal meter between the dish and the DVB-S, it lit up, so power must be getting through to it, and it makes a sound when I turn the little knob about half way, so it must be getting a signal.
Both the AverMedia software and MediaCentre find the device, and try and tune it - but with AverMedia, I end up with no channels, and with MediaCentre, I try to tune it, I go through the set up TV signal, past all the obvious stuff,
Optus D1 (NZ)
Custom Single Oscillator
Frequency - 10750
(signal quality shows nothing, basically)
I still get my list of channels, but with no data, and if I try to select one, it says the tuner is not ready or there is an error.
I have tried all sorts of things, trying the universal and the dual oscillator options, transponder scanning, but nothing seems to get me a signal through.
Scratching my head now - any ideas?
Thanks.

[Mod(Nety):Moved to correct sub forum]