Unable to connect to X server

[fish47]

Laptop:
Lenovo V460

OS:
Ubuntu10.04

Kernel:
2.6.34-020634-generic

RelatedPackages:
udev 151-12.3
libgpod-common 0.7.93
libudev0 151-12.3
makedev 2.3.1-89

Hi everyone, recently, I come up writing a udev rules to disable the touchpad while I use the mouse. But I came across a strange situation as the title. I have tried the "synclient", but it doesn't seem to work at times.

synclient TouchpadOff=1

I lean how to do that from the web-site below. I have read it completely at least twice.

http://www.reactivated.net/writing_udev_rules.html

I want to analyze how the udev works, so I the command below to grasp the information, you can check them out from the attachments.

sudo udevd --debug

You can see the corresponding message that present the situation at LINE 100 from add.txt. Like this.

1325675158.824063 [4626] util_run_program: '/usr/bin/xinput' (stderr) 'Unable to connect to X server'

And here is my udev rules.

ACTION=="add", SUBSYSTEM=="input", ATTR{name}==" USB OPTICAL MOUSE", RUN+="/usr/bin/xinput set-prop 13 125 0"
ACTION=="remove", SUBSYSTEM=="input", ATTR{name}==" USB OPTICAL MOUSE", RUN+="/usr/bin/xinput set-prop 13 125 1"