aluminim foil is not astheticly pleasing, but several layers of it will greatly reduce the interference. Another option is to use a Side panel from a computer case.
I have a 27inch tv that sits about 5 inches above my 3 19inch monitors, and I have a few layers of foil and a side panel from a case between the monitors and TV, there is still some interference, but its not very bad at all any more.