[xmonad] odd interaction between xmonad and tsclient

I sometimes use tsclient/rdesktop to connect to a Windows box. I find that once focus is inside the remote Windows desktop, any xmonad command depending on the use of the mode key (the Windows key, in my case) fails. The key press of the Windows key seems to go to the remote Windows box rather than to the local X system. I say this because pressing the Windows key immediately pops up the Windows start menu. I happen to run the gnome panel with a workspace switcher, and so can use it and the mouse to break out of the remote Windows session, but that seems inelegant. Has anyone else encountered this problem, or have a solution for it? Thank you, drc