[xmonad] Screen workspaces not working on new Ubuntu 8.04 amd64 install

[Adr3nal D0S]

I was using Xmonad quite successfully on Slackware 12 and 12.1.
However, we were recently forced to switch to 64-bit Ubuntu 8.04 at
work.  Under Slackware I was able to have a separate workspace on my
left and right monitors. With Hardy I have a single workspace that
spans both monitors.  I've even gone so far as using the same
xorg.conf on both and the hand-built Xmonad I was using under
Slackware, yet the behavior persists.  Comparing the xdpyinfo output
and the xorg.0.logs the only major difference that I see is Hardy has
DRI working and a few newer versions of some X modules.

I am at a loss as to what could cause this.  But it makes Xmonad
useless to me and I'm dying in Gnome.

Please help.