Monitor Switch Box

Hey guys, I just bought a monitor switch box and two decent vga cables. I am running 1 monitor on the I/O and a computer on A and a Computer on B. When either both computers are hooked up or just one, I get this weird ghosting effect. Now i have gone through 2 differnt boxes, and both do the same damn thing. The monitor connected to the computer looks just fine, but when through switch box, doesnt. And these boxes work, casue on a differnt setup at work, with a KDS 17" standard cheapo its fine. My monitor is a NOKIA 17" 447xpro which is Apature Grill .25mm dot pitch, around 2 years old. Any Suggestions out there. It does this on all resolutions. On both video cards. Running win2k on both machines.