[xmonad] XMonad inside Virtualbox inside XMonad

Hi, Somehow XMonad and Virtualbox beetween them conspire to prevent the key I use as my XMonad modifier to be passed on to the guest OS (even when Virtualbox' key capture prevents the host's XMonad from seeing it). I have checked this by running xev in both host and guest and comparing what they see: all other modifier keys I can think of, get through to the guest except for the XMonad modifier. Obviously this makes it impossible to use XMonad sensibly in the guest. Any ideas about how to get around this problem? Thanks.