Comment 2 for bug 1068465

I think the trigger is your desktop size: 2560x1600 and 1920x1080
And therefore the real bug is probably bug 1064834.

Please test reducing your desktop to a single monitor, briefly. Does that help?

Either way, please try the fix proposed in bug 1064834:
https://bugs.launchpad.net/unity/+bug/1064834/comments/7