sounds like a bios or a onboard video chipset issue. looked online at your mb there a few new bios they all say beta bios on them..i would try update your mb and see if that helps. the other thing is you have onboard video chipset.
MD 790GX Chipset with ATI Radeon HD 3300 Graphics
try turning the onboard video off. and setting the gpu as the first boot device. if it still acks up then it a bios/mb issue older mb tryingto run a newer card.
hey man great thanks for the info. finally someone who reads and doesnt say " well ur psu is too weak" or some bull like that lol. i have done a bios update on my mobo. i have asked many computer geeks and they all say even if an older mobo has a new card in it will work as long as the requirements are met. really the card works great for the most part. only when the certain things stated in last post happen. the weird thing is the power switch thing to fix it. i only have to do it once. i can turn off the computer leave it for a week and come back and it fires right up