U3014 HDMI on Macbook Pro 15" Retina Bootcamp Windows 8 Pro

Hi,

1. I have been using the monitor since February last year. Suddenly this morning the monitor refused to display in 2560x1600. NOW it only capable to display @ 1024x768. 
2. At first I suspected my HDMI went kaput so I changed another HDMI cable (1.4v). Still only manage to display 1024x768. 
3. I managed however to do custom display 2560x1600 but the display is terrible. It's as good as useless.
4. I have performed reset. Reboot machines a few times. Turn on-off the monitor. Still the result is the same.
5. I have also tried to install DELL calibration utilities software and driver - result still the same.
6. Dell calibration software cautioned me though that the it's not able to detect U3014 monitor connected.

What else do I need to do to confirm that the monitor has problem that needs to be repaired?

FYI, in MacOS, I'm not able to display anything on the U3014.

Thanks.

Edmund