[xmonad] focus but hidden

Occasionally I will have 2 or more windows on a workspace and fullscreen tiling and when I switch focus, the red border on the visible window goes away, but it does not switch to the other window. My only recourse then is to move the windows to other workspaces to see them all. To get the workspace to behave correctly I have to delete them all or move them all. I am running Ubuntu Hardy and aptitude shows that I have xmonad 0.6-3 installed, though $ xmonad --version shows 0.5, which I find disconcerting. I have to say, I enjoy xmonad so much I am willing to put up with this inconvenient behavior...but it would be nice to fix it. Thanks for any help. Peace, David S