I have a BenQ XL2730Z that I've been using for a while now, never had any problems. Now I suddenyl can't go over 60hz through displayport. Uninstalled drivers as well as possible, reinstalled 2 different versions, no help. If I plus my DP cable into my mobo it works perfectly at 144hz, so it's definitely the GPU. When going into additional settings in the AMD drivers, it often says something like 'there is a problem with the connection between your computer and the displayport cable. You won't be able to use higher resolutions'.
Anything that might help, or am I out of luck.