maybe try using 'driver sweeper' to remove the old installation of video card drivers.
this can help with problems like that.
and if it doesnt, i would suggest keep trying different video card drivers from a number of different versions.
dont necessarily stick to the same major update number.
for example.. nvida uses 240 , 250 , 260 major version number.. then there is a dot and another number to show the minor update number.
you could try different minor numbers and different major update numbers.
if this doesnt work.. it makes me think maybe there is a profile being called upon for your monitor that is incompatible.
maybe the resolution is too high or the refresh rate is too high or too low.. and you have to delete the monitor profile before getting it to work.
you said you tried a different resolution.. but you didnt try a different refresh rate.
i would try this too.
and if that doesnt do it, maybe your graphics card is somehow failing.
i know it doesnt make any sense that it worked a couple hours ago and not anymore.. so i wouldnt put this on the first of things to try, but maybe the absolute last thing to try.
if you have an old hard drive, you could always install windows xp on it and see if the video card works with the television again.. that would prevent you from changing the video card with windows 7 .. but it would inevitably bring you to the decision 'maybe my video card hates windows 7 ... or maybe windows 7 hates my video card'
probably a driver problem though.. as ugly as it sounds, since you shouldnt be getting a signal for 1 second and then getting no signal at all.
but
maybe that is how your television works when the refresh rate isnt supported?
some will jump to 'no signal' when the desktop is supposed to show.
i dont see why the television wouldnt show the desktop for a second and then say 'no signal'
but
'no signal' is not the same as 'refresh rate too high'
my CRT monitor tells me 'no signal' and 'refresh rate too high'
but that doesnt mean your monitor will say both.
i think try the refresh rate first, then ask around if windows 7 has custom profiles for the monitor.
then i would move on to different drivers.
i know i had used a program with windows xp that created a profile, and it prevented the graphics card software from seeing all of the refresh rates available for my monitor.
got rid of the profile and the refresh rates were listed again.