[J65nko]

The easiest way to solve the permission problem is to create a "mount" partition, inside the home partition. I am lazy to type so I use a directory called "U"

 $ sudo mount /dev/cd0a U

I modified your script:

#!/bin/sh

DEVCLASS=$1
DEVNAME=$2

case $DEVCLASS in
2) # disk devices
        case $DEVNAME in
        *)      echo $(date) : DEVCLASS: $DEVCLASS >>/tmp/debug.attach.txt 2>&1
                echo $(date) : DEVNAME : $DEVNAME >>/tmp/debug.attach.txt  2>&1
        esac
esac

When I plug in an USB memory stick I get this in /tmp/debug.attach:

[adriaan@hercules]~: cat /tmp/debug.attach.txt                                 
Wed Jan 9 02:41:21 CET 2013 : DEVCLASS: 2
Wed Jan 9 02:41:21 CET 2013 : DEVNAME : sd0

When I put a CD or DVD in my DVD rewriter nothing is being written to that file.
Even the following attach script does not produce anything on inserting a CD.

#!/bin/sh

cat <<END >>/tmp/debug.attach.txt
$(date)
--------------------------------
$(env)
--------------------------------
$(set)
--------------------------------
END

So no event is happening, thus no running of the script