DIYGuy - if it is below 0C up there it'd be great if you could just quickly test your controller one day. All you need to do is apply throttle until motor amps exceed 175A or so and see if desat trips. Whether it does or doesn't, updating to 1.3 is a really good idea since it fixes a minor bug in Quiet mode that Qer found (and which we *think* might be the cause of the cold weather desat problem). Unfortunately, we don't know for sure since none of those affected has reported back to us and we can't duplicate it ourselves.
gdirwin - my first suspicion was frost, too - and that may be the cause for the Zilla because it isn't really sealed at all, but the Soliton1 is fairly well sealed (if the ethernet cap is on, anyway) and the desat error goes away as soon as the heatsink temp exceeds 0C (as reported by the thermistor). If there was frost inside the controller it would take a long time for it to first melt and then evaporate, especially at just above freezing, so I don't think that's a likely cause.
A much more plausible explanation, - besides that bug in Quiet mode - is that a substitute for a part we could no longer get (this happens all the time and it is probably the most frustrating part of my job) isn't behaving quite right at cold temperatures. Once again, that it goes away once the temperature gets above 0C kind of argues against that, but, well... stranger things have happened.