xorg upgrade error

[Tim <alt.os.linux@gmail.com>]

I'm getting the following error after a recent apt-get upgrade:

xserver-xorg failed to preconfigure, with exit status 10
(Reading database ... 103577 files and directories currently installed.)
Preparing to replace xserver-xorg 1:7.0.1
(using .../xserver-xorg_1%3a7.0.15_all.deb) ...
dpkg: error
processing /var/cache/apt/archives/xserver-xorg_1%3a7.0.15_all.deb
(--unpack):
 subprocess pre-installation script returned error exit status 10
xserver-xorg postinst warning: not updating /etc/X11/xorg.conf; file has
   been customized
Errors were encountered while processing:
 /var/cache/apt/archives/xserver-xorg_1%3a7.0.15_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

This is a recent install of debian sid. I can't find anything about this
error in any of the logs and google doesn't find anything relevant.

How can I go about fixing this?
-- 
Tim <alt.os.linux@gmail.com>