Humidifier coils freeze

I believe a dehumidifier is supposed to operate in temps above 60 degrees. Even though your house is warmer than that, the air entering the dehimidifier may be getting into that range due to it being on a basement level etc. This is perfectly normal and is not a malfunction with your humidifier.

Your options are to either place the dehumidifier closer to a heat source in order to keep the air which is entering warmer. (I've even heard of someone placing a light bulb in front the unit during winter to warm the air slightly as it enters). Because the dehumidifier's coils get cold in order for it to collect moisture from the air, if they are freezing, giving the unit a rest for a few hours every few hours may allow the coils to thaw in between and prevent them from reaching freezing temperatures while running. You could use a timer to accomplish this, but you'll want to insure that it's a commercial grade timer in order to handle the electrical draw that the dehumidifier requires.