Thank you for all this information.
I noticed you mentioned you are using a Dual DVI link cable. Our graphics controllers support Single DVI link so can you please try a Single DVI cable?
This can do the trick.
Single link DVI does not offer modes above 1920x1080 @ 60 Hz, so trying such cable is pointless, it will not allow me to use 2560x1080 @ 60 Hz. LG intentionally puts a dual link DVI cable in the package so that their displays worked fine.
Anyway, if HD4600 does not support dual link DVI, this explains why this problem occurs. I wish this information was written in BIG RED LETTERS on every Intel Inside sticker so everyone knew that. :-)
LOL! Wow. See, this just shows you how LITTLE these employees at Intel know. The hardware is built to use dual link cables, yet this employee thinks the single link will be better? LOL!
Intel: Get your **** together. Let us set WHATEVER refresh rates we want. It's YOUR SOFTWARE that's limiting us, NOT the hardware that WE ARE PAYING FOR. It's because of this error that I will NEVER purchase an Intel product ever again and I will continue to warn all of your customers on this website to stay clear in the future. How's that for business?
Thank you very much for your feedback; however, I disagree with you regarding the Dual link DVI. Our controllers support Single Link DVI only.