So i got my second monitor a while back last year and it was working fine. I just recently installed a new driver for my HD Radeon 4670 and the monitors both still work. Its just at the start-up my second one works fine for about 3 minutes then it just shuts off and i have to manually extend both displays again(My main monitor is fine). I think its the drivers but Im not sure any advice?
Anytime that you have a problem with something in the computer and you just did a change in it then it's a good chance thats the problem and in your case , yes I think it's the drivers and you can try deleting the drivers and then reloading them and if that don't work then try deleting the drivers and the video card and shutting down and unpluging the psu and clearing the cmos. Then reload everything and see if that changes anything.