Problem on X application [1]

When i run my X Application on PC have installed XManager, i didn't see the resoult-- window, buuton .. etc. When i run command in XStart
, i got a message " Can't open Display !!: 0 ". but i can run any command in unix OS on my PC and the resoult is correct!
i check the "DISPLAY", it is "ass001:0.0" . ass001 is my pc name( equal IP address ) defined in file /et/hosts on the UNIX Server machine. those two machines are in the same segment.
Pls tell me why and how to do?

Windows version and Server machine might be a clue to the solution of this problem.

- Sue