9200/9800pro conflict...help please.

Hi all,
Recently my 2 Radeon video cards began conflicting,i have a 9200 and a 9800 Pro DDR each one of them conected to a monitor,if there both installed then the 9800 pro begins flickering,pixels which overflow in each other and a very stuttered image,while the 9200 will work perfectly,but when i take the 9200 out the 9800 pro will work perfectly.they worked perfectly for 6 months no probleam at all,now suddenly they dont work togther,i have formatted my pc but still the probleam exists.i am a pc noob,any help is apprecited,ty in advance for your replays!

Current specas detalid as i can)
Windows XP Pro.
MSI 865PE Neo 2-PFS Socket 478.
1.2GB.
Intel 2,8Ghz 512kbc 800Mhz fsb.
Zalman CU Silent s478/s462cpu cooler.
Maxtor SATA 8mb cache diamond max 9plus,120GB 7200rpm Fluid Bearing(hdd) SATA Hdd.
Antec Super Lanboy Case.
4.12 ati catalyst drivers.