Originally Posted by Schoenfeld
If two CRT monitors are standing next to each other and they operate at different frequencies, then the magnetic field of one monitor influences the picture of the other monitor. You are not seeing a problem of the flickerfixer, but you are seeing a common problem with the old tubes. If you want to play a little, just take a magnet and move it close to the picture of your CRT and enjoy the colours ;-)
Flat screens are by far more immune against magnetic fields.
I would have to concur with Jens on this assesment. Those crts, especially the big ones, have very strong fields. Also grounding problems on the circuit if they are both connected to the same can make the wobblies too.