X -query localhost:1
should be

Code:
X  -query  localhost  :1
(Space between localhost and :1)

I tried it yet with an unchanged Knoppix box (192.168.1.99). All I had to do was:

1. In /etc/kde3/kdm/Xaccess change
#* #any host...
to
* #any host...

2. In /etc/kde3/kdm/kdmrc set
[Xdmcp]
Enable=true

After /etc/init.d/kdm restart I was able to
X -query localhost :1
This gave me a logon screen on vt8, vt7 was my original kdm screen.

From another box (192.168.1.100) in runlevel 3 (no X)I connected with
X -query 192.168.1.99
If there is already a X running I use
X -query 192.168.1.99 :1

Works with these two changes above.

Good luck
Ciao Martin