Had the same issue and looks to me more related to menu items offset in the video than a mouse problem. See ticket 0000822

this comment solved my problem too :
(0002807) Jarhead1145 (reporter) - 2013-03-07 15:39

http://feedback.arma3.com/view.php?id=901#c2807

I think I know what you're going through, I had this issue as well. Here is what
you do, go to your Arma 3 folder and right click arma3.exe then click
properties. Click the compatibility tab, then look for "Disable display scaling
on high DPI settings" and then click the check box next to it. Hit Apply and
then OK then try to run the game.

Managed to start activating the play option without seeing it, in offs1.jpg and offs2.jpg you can see my screen and the offset of the mouse (which I manually draw in red, as the mouse pointer is not recorded by fraps).
As you can see the offset increases moving away from the top left corner.

Also, not the full screen is visible.
This looks like the interface size is bigger than the actual screen, there might be a menu option to correct it, but I cannot see it since I cannot activate the menu.

Attached screenshot shows my initial screen. Menu is not visible

The problem is also in windowed mode.
Mouse acts in a position which is different from the poitner.
However alt-tabbing to another application and back, suddenly the mouse position seemed to be correct.
Switched to full screen, now I can finally see the menu, but again the mouse action have an unpredictable offset.