4K and UHD is indeed 30Hz over HDMI. 60Hz is from displayport today.
Most folk don't have enough GPU power for 4K or UHD play so we change it to 1080p 60Hz. Try that.
PS added with moderator edit: Source for that statement is at https://www.google.com/#q=30hz+4k+uhd
The reason I tried to sell this monitor is because of the mouse lag. But it seems it will only run at 30 Hz in Windows 7 Pro 64-bit while using a video card that supports 4K. Is there a way to make it run at 60 Hz so there is no mouse lag anymore?. Thanks.