Well not much more I can say. I move my mouse while in game and it doesn't get locked in game, it just goes from monitor to monitor to monitor. It's really hard to play while trying to keep my mouse on the game screen. My friend has 3 monitors as well and he has the same problem, but he can't deal with it at all and refuses to play till its fixed.
Win8.1 Pro 64-bit OS
CPU: Intel 4930K @ 4.5ghz
MB: Asus Rampage IV Black Edition
Memory: 16GB Dominator Platinum 1866
Video: Dual EVGA GTX 780 6GB SLI
HD: (2) Samsung 840 EVO 250GB RAID0
HD2: WD Black 1TB
Monitor: Asus 278Q 28" UHD 4K @ 60hz
Monitor 2: Asus VE247 23" 1080p @ 60hz
Monitor 3: Asus VE247 23" 1080p @ 60hz
Mouse just doesn't stay in game.. travels outside of game and minimizes if I click outside of game... not sure what other info I can give you, if you have something specific to check or do, please let me know.
FuMA