There is a lot of information at
http://www.short-media.com/forum/showthread.php?t=19549 about this problem. They are talking about Dell P1110 but the monitors are probably very close. I just fixed several Dell P1110 monitors with the same problem. The fix is pretty easy, however, if the monitors are not exactly the same on the inside, you will need someone who can tell you which resistor to replace.