Reflection off of screen
Plasma TV's are known for their glare and reflection issues, you can still fix it by buying a third party anti-glare filter and applying it on your television. For example, "ViewGuard" makes filters that goes up to 65" in size. It is not cheap though, depending on the size of your television.
Of course, the best solution is to adapt your room accordingly. If the glare is caused by the sun light coming from the windows, installing curtains on your windows or moving your television to a better spot is a very effective way to reduce the glare and the reflections on your television.
If the glare is caused by the room's lights, the best solution is to install ceiling spot lights with a dimmer.
Hope that helps!