Sounds like you are not getting 12V power from the battery to the breaker panel - the slides/landing gear (and a few others) run off the DC bus bar and autoreset breakers and the lights/refer/water pump run off the DC breaker panel. THe 12V supply from the converter seems to be feeding the breaker panel though.
You'll have to check your specific wiring but I would check to see if there are two 12V feeds to your breaker panel, and see if one from the battery (or disconnect if you have one) is loose and not making good connection. Sometimes when it gets colder outside, the connections that are loose/limited, or wire problems show up with a colder environment. The fun of troubleshooting electrical.
Good luck.
Brian