Once I played it on a TV - one portion was way too dark. Can you adjust the brightness/contrast to one area. I tried highlighting the area and then dropping in the Video FX brightness control, but on the computer - there was no change. Is the change not viewable until i view on TV again?
You can also keyframe effects so you should be able to make the effect "none" at some places and in force in other places based on the keyframes. You will wnat to change the animation setting to "Hold" under the right click menu or you could phase it in to make the switch less obnoxious.