pc prob

ok here it goes, i just put in a new motherboard about 3 weeks ago , and about a week ago my monitor started going black saying auto detecting signal. sometimes it comes back , and sometimes it doesnt , it goes in to power saving mode and wont come back on until i hit the power button a couple of times. it happens alot when i am using high cpu usage .  after i get it to come back on, my computer usualy freezes out. two times it went to a blue screen saying windows xp needs to shut down and all this other stuff  . ive tried to do research on it but i cant find anything. it wasnt doing this with the old motherboard. i just dont know if it is a bios prob or a my video card or what. i dont think it is my monitor since it wasnt doing it before.