I've been on a four day hunting trip and had a problem with two Aimpoints! One, a 3000, had failed before but has been working properly for several months. The other, a Comp M, failed this trip. Both would either dim or go off entirely when a round was chambered or fired.
After considering sending both units to Aimpoint for repair (and the shipping cost, downtime, and need to rezero two rifles) I decided to clean the switches since the Aimpoints aren't nitrogen charged. To someone with similar problems there's an easy fix. Loosen the allen screw(s) on the brightness knob and remove. Remove the small hex nut and washer plate that retains the switch. Next, remove the end cap that the switch mounts in by unscrewing it. This takes two small pieces of drill stock inserted in the holes in the end cap. Pull the switch unit out being careful not to break the small wire attached to it and remove the rubber gasket. Wrap the unit in a rag and spray a non-conductive cleaner (I used LPS ZeroTri) into the holes in the switch housing. With the knob temporarily reinstalled gently pull (to seat the contacts) and turn the knob back and forth to clean. Rerinse with cleaner and reinstall the parts in reverse of disassembly.
This process fixed both my sights and as a side benefit, both are brighter than before. I wouldn't leave the sight open for long to prevent moisture from getting into it. Don't start the job and finish it next week...