Dual Display on 8500 causes lines and spots

[lastig21]

I just set up my 8500 to use dual display. I have a vga lcd on the vga connector, and a crt using the dvi-vga converter. The lcd is my primary display. Anytime I type or move my mouse it causes lines or little black boxes to pop up on the crt. Any idea what would cause this, or better yet, how to fix it? I'm using the 6.13.10.6015 driver in Windows XP.