Comment 1 for bug 258821

Just filling in a little more details about this:

xmonad 0.6 in hardy, and 0.7 in hardy-backports does not support Xinerama.

This is caused by libghc6-x11-dev 1.4.1-1 in hardy (source package "haskell-x11"). The package is simply built without xinerama-support. In the current deibian/intrepid-version 1.4.2-1 this have been fixed by adding a build-dep on libxinerama-dev, but note that this is also a new upstream version.

The backport is also a bit tricky. All xmonad-packages for some weird reason have hard coded exakt version dependencies on 1.4.1-1. So after backporting haskell-x11 you cant just rebuild xmonad and xmonad-contrib, you have to edit their control-files and update the version everywhere first. (This would of course also be required if haskell-x11 should be SRU-ed instead of backported)

With modified dependencies the resulting packages work fine. I have been running my own backport of haskell-x11 1.4.2 xmonad+xmonad-contrib 0.7 a while now without any problems. No changes was made except the dependencies as mentioned, but I could post the trivial debdiffs if necessary.