Blank screen on dual screen setup

[Bavaria]

I have a 2 monitor setup, both are Samsung 2243 21.5 inch monitors, I turned my Pc off last night when both monitors were working fine, turned it on today and only one screen is working and the other is showing a box saying check signal cable, I moved the dvi cable from one port to the other and it works, but I want to narrow down the problem, its most likely the port by process of elimination, but im a noob and want some advice from people who know more.
why would it just die without any sings. ps its a nvidia GTX 580.
any other test you guys think I should run to make sure before I have to spend some cash on a new GPU?
thanks a ton.

 

[Bavaria]

I seem to have gotten a solution, the GPU was reaching temp of 71°C So I cracked a window and let some air through, had a GPU temperature widget installed and it went down to 60°C and everything is back to normal.
Maybe this solution might help some, will get an extra fan tomorrow.