Exactly the same issue today with a brand new Promethean PRM35. Problem was with the power supply connecting the laptop which we use to drive the projector. It's a two year old Toshiba machine and by replacing the Power Supply with one from a brand new Toshiba laptop the issue is resolved and no more flickers. The power supplies are the same output the only difference is the old one has a three pin connection from mains to the transformer the new one only has a two pin connector. Might be worth a try if you are experiencing this problem.
