access to Xserver refused ???

[belahcene <belahcene@iap-cu.dz>]

hi,
I used ssh -X  to connect to remote machine ( running sarge debian ),
but couldn't run  any graphic  command  , for example

user1@semAmphi:~$ lyx
lyx: cannot connect to X server
user1@semAmphi:~$    

Normally the -X option gives this possibility
I add the host to my display with, xhost +, but same problem


while  I can do it to another machine ( running knoppix 3.7) like

bela@BelaPc:~$ lyx
Xlib:  extension "XFree86-DRI" missing on display ":0.0".

in spite of the message, I got the windows

Is there a special configuration for ssh ?

best regards
bela