This is something odd, when a contentpane is undocked and moved into a floating state PRISM V4 RegionManager seems to loose a reference to that ContentPane's injected region, causing some of my code that depends on this to fail.

Note: Re-docking seems to add the region back into the RegionManagers collection.

Any suggestions? I can probably figure this one out or a way around it but i wanted to bring it to your attention and see if perhaps you already have a solution.