[Xmonad] cut & paste between xmonad and macosx appl

Hi, I've been running xmonad on my macbook pro for a week now, and I really like it. The only knack I have is that cut-and-paste between mac appl to xterm/urxvt and vice versa stop working. Does anyone running xmonad on macosx 10.4 having this problem? Or did I overlooked something in my setup? I've tried different setting in my X11 prefs without effect. Hope someone can give me some leads. TIA, Quan