Can I install a LCD or plasma TV above a fireplace?
Our friends at Regency Fireplaces have answered this FAQ for us…

TV above a Regency fireplace
When installing a TV above a fireplace clearances to combustibles around and above fireplaces are not the same as clearances to TV’s and other electronic appliances. Televisions and electronics in general are manufactured and assembled using many variations of materials and are subject to damage from far lower
temperatures than wood etc. Many of these materials can be affected by temperatures far lower than those approved and considered “combustible”.
To be safe when determining what clearances are required from a TV or other electronic device to a fireplace, you should find out from the manufacturer/distributor of the component, not the fireplace. Clearances to combustibles around and above a fireplace can be well within certified specs but could still possibly be too close for TV’s and other electronics.”