Condensation happens when air cools and becomes over-saturated. Water is wrung out of it like a sponge. Heating the air helps, certainly. But there's a catch: You sweat and breathe out moisture, so if you don't allow fresh air inside - which brings in more water-soaked air, unfortunately - then you still humidify the air and cause condensation.
That's why defogging a windshield can be such a darn pain.
So your best bet is to keep the interior air as warm as you can and allow in a small, steady stream of air to carry away humidity. Like Tony said, crack open a roof vent. In some cases, you might be better off running a powered fan.
If that's not working ... well, sometimes Mother Nature just doesn't cooperate :p
You can also buy a moisture absorbent like Damprid.
Interesting that the condensation formed on the upper walls, though. Are your walls skeletonized or stick-framed? Those wall designs tend to allow condensation much faster than a true foam-core wall.