I had a problem with my monitor as well ( a 22" HP w2207h ).
I was recommended by somebody to turn down the brightness because the default one was too bright and would hurt my eyes, so I did.
But by turning it down about 50%, my eyes were actually struggling to read web pages, and I was getting tired and full of headache in a matter of half an hour, let alone long playing session at Bioshok 2 !
So one day I decided to turn it up again, and my eyes stop to hurt almost immediately, as the improved contrast ( especially the familiar black text on white background ) was somehow easier on my eyes.
I suspect that in the long run it wouldn't be very healthy for my eyes, but hey, a lot of things in life aren't healty but we can't leave without it !