Interesting tip I came across on another forum. Note I haven't tried this myself because i have CRT. If you mess your screen up don't complain to me, use at your own risk.
Having said that many people have had success with this. Gently "massage" the area where the pixel is dead. Repeat if it doesn't work up to 4 or 5 times. One thing to note from the posts I've seen is that it doesn't have permanent effect all the time, some mey die out again.