all, I've been trying to set up a touch screen but am having a few prelims, he's what I do

1. modprobe usbtouchscreen
2. modprobe evdev
3. cat /proc/bus/input/devices

No touch pad is detected, however if I disconnect the screen USB and reconnect it appears.

I: Bus=0003 Vendor=0596 Product=0001 Version=0410
N: Name="3M 3M USB Touchscreen - EX II"
P: Phys=/input0
S: Sysfs=/class/input/input3
H: Handlers=mouse1 event3 ts1
B: EV=b
B: KEY=400 0 0 0 0 0 0 0 0 0 0
B: ABS=3

However the screen touch positions are are off (eg touch bottom and it mouse is at top ect). Can anyone help me out? First why do I need to dis and re connect the screen for it to be detected. Second how can I calibrate it.
I've seen internet notes on using xorg.conf, but when I try it just crashes xorg.

I'm running on Debian etch.

Thanks