"Cannot open display" or XDMCP problem ?

[Clive Butler]

Francois,
  On your Win95 laptop, it looks like the xhost does not
get a chance to run until after the XWin server has been
through its XDMCP attempt (by which time it's too late).

  Can you try adding -ac to the XWin command line instead of
using xhost (temporarily..)

  You should also be able to set DISPLAY to 127.0.0.1:0.0
(or even just :0) on the PC rather than have all the local clients go
out over the network and back..

  Clive