This issue is not isolated. Currently, you can not rebind the mouse buttons to anything else accept what the default says, because they are hard coded. For example, I bind left click to move forward, and right click to fire weapon. First I unbound both buttons, then bound them to the functions I wanted. The problem is once they were 'bound', left click DOES move forward, however it still tries to fire whatever weapon you have readied as well... so with a melee weapon equiped, left click walks forward AND swings the weapon when you hold it down. Right click, which is SUPPOSED to be bound to fire, doesn't do ANYTHING (I bound look down sight to spacebar, and zoom in to the w key). I will link my original report, as it seemed to be the first one reported. The devs have refused to even acknowledge the issue despite MULTIPLE reports of similar issues both here and on the troubleshooting thread in the DayZ forum.
http://feedback.dayzgame.com/view.php?id=343 uno online[^]Go ahead and upvote it, as the issue you are describing is the same issue.

Same issue with Windows 10. It was also solved after I run as admin.