With the monitor that's moving, is it the monitor that you selected for the Eyefinity grouping? Is it a Primary monitor?
It's such a weird situation that I'm grasping at straws here. I am just wondering since:
"Primary monitors" get some pretty "special" treatment, so if it's the same monitor moving, it may have some special attribute about it. If you chose that moved monitor as the "Select a monitor to make a display group", then it may be moving that monitor thinking that the Eyefinity grouping shuffled things around. I'm at a loss, but try a different Primary monitor or try to create a new Eyefinity group with a different "main" monitor.
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