[Xmonad] mod-{w,e,r} don't work when OpenOffice.org has focus

I have two heads, the left one shows workspace 1 which is in full layout and contains OpenOffice, Firefox and Adobe Reader. The right head shows different workspaces as time goes by, usually in tiled layout. Now it turns out that OpenOffice somehow grabs focus so that mod-e does not work to switch to the second head. I can still do mod-j to switch to a different client on the left head, and then mod-e works. But when OpenOffice has focus and after I click into it, then mod-e will not work to set the focus to the right hand head. Has anyone else observed the same? Is there a fix? What can I do to help debug it? (I don't grok Haskell, though I'm trying.) Kai