[SOLVED] "No Signal" To TV When Playing Certain PC Games

Yesterday i downloaded a demo for a game called hoard after it installed steam automatically downloaded some drivers for it like gamesfor windows live direct x updates etc. when i started it up i was met with a black screen and the words no signal my computer locked up i couldnt exit out of the game even though i could hear the menu music

so i deleted and reinstalled the hoard demo after restarting my pc but got the same result. i just deleted the game and continued playing the games i usually play like fallout new vegas and left 4 dead 2, i thought that maybe there were some bugs in the demo or something as this was the first problem of this kind i have encountered on this pc.

But today when i tried to play spore i got the no signal screen it is the same as before but i can exit out of it with the windows button

i dont know whats going on, i have tried many things updating video card drivers, updating to the latest windows 7 service pack 1 but nothing works

there is no reason for hoard not to work it is not a graphic intensive game in the slightest nad i have played spore many times before
oh and by the way my graphics card is a ati radeon hd 5570 but i dont think its a problem with the card overheating because i can play fallout for hours and i have never lost signal while playing it