Dell UltraSharp 1800FP - display leak - blue craziness

Hello there, when I turn my Dell UltraSharp 1800FP on, it may work fine or it will go weird blueish effect. I tried all kinds of things - without the VGA cable, the monitor shows the "self diagnostics display" and right side of that box is "leaking" blueish, hard to explain for me, but someone there will understand. It could stay like that and run up and down with nicwe clear NO SIGNAL box or it shoots and leaks the color just on the side of that box or goes crazy all over the display. As I said, hard for me to explain... is there anyone who would know what am I talking about and help. Please...