Cortex overheating

I have a cortex that is getting hot under the following conditions; cortex is turned on, and using USB only communication. When I turn on the power to the cortex, I get all three lights turn yellow. I’ve tried re-updating the cortex and robotC firmware, I used a different USB cable, a different battery, and checked for bad wires which could cause a short. Another strange symptom is that all the sensor values for pots and light sensor are about 10 percent of what they should be. I tried 4 pots all gave the same range of 0-250ish instead of up to about 4500, the light sensor is only going up to about 150 instead of around 1000. Any ideas?