Possible moniter problem?

Once and a while my moniter will go black and say 'analog one, no signal'. It didn't happen that often, but when it did it always happend in the middle of a fight (usaully at our 10th game in ta ). Recently my computer died and i took it in and got it cleaned up. Now whenever i play guildwars within 2 minutes of getting on a charector this happens. If anyone knows what is wrong or even what could be wrong, that would be great.
note: this only happens when i play gw

edit: also i get this: out of range
h. frequency: 23 hz
v. frequency: 37 hz

Well looks like your resolution is set to high for the monitor or you have a failing cord. (the 1 that runs from the monitor to the cpu).

But if you are going to purchase a new monitor I suggest a hp w1907 or better. the picture is so nice it makes me cry, well it is really nice and the wide screen is the way of the walk. I'll NEVER go back to a square.