LOL Thats funny. My Thread is so old and so undead.
I tried many things to solve that issue, and something worked. But I was unable to figure out the exact trick. Unfortunately although i set GPU priority in BIOS to Onboard, every now and then after restarting the PC the Monitor stayed black and shows neither a picture at the onboard port nor at the Radeon card. Now I only use the ATI Card and everything is fine except of a laggy system while mining.