This just might fix this problem. I updated the aREST.h file. It was way out of date.
I just see this thread and realise I had a bunch of NaN values myself yesterday on GroveWeatherPi... Are driver updates "global" on github or isolated by project? Will I have to update stuff on my GroveWeatherPi also?
I, too, am having similar problems. The unit hangs anywhere from 12 to 72 hours requiring a power cycle to get it going properly. I get date/time like 85/165/2009 37:165, Outside humidity NaN, Indoor temp: -216 F, BP 53.78. When the unit hangs it stops reporting to underground weather EXCEPT for wind speed, wind gust, and wind direction - these value keep reporting. The unit is pingable, but can't provide any data past the first time I query the unit with the OurWeather page. I am running on firmware version 33. This problem has happened on 3 different Ardurino weather boards. I tried to compile 34, but it wouldn't compile. When will this be fixed ?? It is obviously a relatively common problem for other users!
Hey did you ever manage to discover what was this? I am hitting the exact same use case but my system is in a rather inaccessible place so hard resets require me to down the breaker for the system and our house internet link