buddy i have your answer
i bought a 23 inch and did exactly the same thing, it was so odd that i had to ship it back to apple. you would not believe it but its the power brick, and the more u unplug and plug it back to use your screen the worse its gonna get, before you know it wont turn back on again... get your apple care out, read the serial number and send that sucker back to California....
aint nothing you can do, displays and ipods are the only products you HAVE to ship back, nobody can repair them other than apple, even if its a stupid power brick.