[xmonad] Copy/Pate?

[Eric]

I finally gave up on all the bloated wm's out there, and have settled on
xmonad after a bit of research and playing around. I'm very happy with
it. The machine is a fresh install of archlinux with xmonad started via
.xinitrc. It seems like a very silly issue to me, but at the same time,
it's fairly frustrating. I'm trying to copy text from one window to
another via X's select/middle-click copy/paste. It seems to work fine
when dealing with the same window, but when I highlight another window,
it either does nothing (if I havn't tried it from that window yet) or it
will paste from the same window. Surely there must be an easy way to
handle this, but after a bit of research, I can't find anything. What's
the easiest way of getting this to work?