Dell GX110 not loading GDM

[Rohan Smith]

OK here is the problem, I have 4 types of client machines. Dell
Optiplex GX110 desktop and tower, Dell Optiplex GX260  tower and  Dell
Optiplex GX270 desktop. All use intel video cards.
When hooked up to the server all of them boot up the edubuntu
bootsplash and loads.
However neither of the GX110s proceed from there... they display a
cursor in the top left hand screen that just blinks. while the other
machines display the gdm edubuntu login screen.
The thin client manager on the server only shows the non GX110 machines.
I tried to edit  the ltsp.conf by specifing:
X_SERVER = auto, X_SERVER = i810, X_SERVER = vesa, X_SERVER = intel

neither work,
also tried :
XDM_SERVER = 192.168.0.254


didnt work either,

[Default]
X_COLOR_DEPTH = 16
 XSERVER            = auto
XDM_SERVER = 192.168.0.254
       SCREEN_07          = startx
       SCREEN_02          = shell

brought up an xserver grey window with a big X which then changed to
rainbow colors....

the other Dells work perfectly!!!

.... any help PLEASE!!!!