Hm, that's strange. Maybe it's not your monitor at all, but your video card ? Maybe you have to reinstall drivers or something so that your monitor knows ... :x
But uhm, here's a choice that's a 19" that's cheaper than the LG one you might get.
http://shop4.outpost.com/product/4200544
And another pretty good deal..
http://shop4.outpost.com/product/3813497