weird monitor problem

A few weeks ago i hooked up 2 monitors to my computer a View sonic and a sync Master they normally work but for some reason the view sonic's screen went blank and produced sound but no image and it wouldn't go back to normal no mater what i did it would show the start up screen for the view sonic but then it would just go blank. Then as time went on the sync master i used went blank too. for some reason i tried out the first monitor again then it started working. but it will go blank again from time to time when i hook it up. then i have to unplug it and wait up to 5-30 mins sometimes for it to work again. the sync master has not recovered at all it stays blank but will play sound. I think the reason why is because the view sonic is a tv/monitor while the sync master is just a monitor... Can anyone give me any thoughts on how to fix this?

 

How old are the two monitors And what kinda video card do you have.

 

Sync Master 2010 i think View Sonic 2011 and the video card is a XFX Radeon HD 5750

 

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