Hi
I have the same problem.
We have a Large Plasma down in the hall. Upstairs in reception we have a 1 computer feeding the reception dispaly and the Plasma down stairs. Via an Video amplifier in reception and a Video amplifier down near the Plasma. We also have a TV feed from the 3rd floor to the hall. When we switch to TV it does not flicker BUT when we use a power point it flickers.
If we use 1 output from the PC to show the powerpoint in the hall and NOT the reception the flicker stops!