Same here, my farm is also watering itself, but I just noticed that I had around 10 nbrs post that they watered, yet in my newsfeed the last ppl shown was over 9 hours ago. I restarted and the newsfeed is the same and my farm is still fully watered.
Iphone 4 (5.0.1 version).
When I look at nbrs farms I can water and it takes my 10 waters but they said they are seeing that their farms are fully watered.