I have dual Evga 660Ti cards on AsRock Extreme 3 (z77 chipset).
 
Had transparent horizontal lines when running 3D Game in SLI mode.
Its sort of like highlighting the sections on screen that one of the cards are generating in transparent Blue color.
 
This was problem since i purchased new card, plugging SLI connector in another SLI slot and no more lines.
 
Was working normal for last 2 years however after not using my computer for 6 months while traveling after plugging computer back on and runing 3D Game in SLI mode started having same issue except its Red lines now.
 
If i switch to another SLI slot i get BLUE lines in other slot its RED lines.
 
Strange thing is that Red Lines only come in Full Screen mode when i have game Windowed even if stretched to full screen it does not show lines. When i Alt+Enter and go full screen problem apears instantly and going to window mode fixes it instantly too.
 
Anyone have any suggestion i am out of warranty now and buying new SLI bridge did not solve my problem.
 
P.S. Cannot take screenshot as when i use FRAPS screenshot looks normal.

That was an easy fix, problem with red lines in full screen SLI mode went away after i reversed SLI Bridge 180 degrees... Wonder why this could have been a problem?
 
I using a flexible SLI bridge. One solid one that i got with motherboard seems to have failed too.

 
I'll try see if blue lines issue have similar fix.