Comment 2 for bug 330258

I fix it by setting $HOME in the script, as otherwise it cannot find .Xautorithy

Now I have the files
/etc/udev/rules.d/11-docking.rules

ENV{EVENT}=="undock", KERNEL=="dock.0", SUBSYSTEM=="platform", RUN+="/home/vrossum/scripts/disper.laptop_only"
ENV{EVENT}=="dock", KERNEL=="dock.0", SUBSYSTEM=="platform", RUN+="/home/vrossum/scripts/disper.dock"

And

/home/vrossum/scripts/disper.dock:

#!/bin/bash
export DISPLAY=:0
export HOME=/home/vrossum
/usr/bin/disper -i < /home/vrossum/disper.dell

Of course you will have to edit according to your local config.