I'm running a RedHat 7.2 system.

I have changed the IP address and it all seems fine!
Except for one thing,
I can not start a X application!! Xwindows self is running fine.

tnx,
Erwin

Can you start the app from a terminal window?

No,

From a X Teminal I have the same result!
X starts fine, i can do a login, but I can not run a application

what output do you get from the terminal window?

How do i find the output?

The X screen on the server comes with no errors,
and the X-WIN32 i have on my notebook comes also with no errors at all.

if you use the KDE desktop then there is an Icon on the toobar. It looks like a command prompt window with a sea-shell over it.

If you can start that, then you should be able to type the application name, such as: xbill , and the probram will either start or display some error. (hopefully)

I can not start the shell.

When you try to start it, it is on the screen for a very short time and it is closing it self in less then a second.

This could be a problem with xauth. This is what checks that apps to make sure they are allowed to run on the X server. There should be a file called .Xauthority in you home directory. Err, I don't really know what happens if you just delete this file though. you can log into a console (CTRL-ALT F5 to get one - CTRL-ALT F7 returns you to the kdm) and type :
xauth info
to see where your .Xauthority file is, you can also modify the file using xauth --help
to list the commands available. Do apps run if you log into KDE as another user?

I ended up with deleting all the files in the /root directory.
after this it was working fine again.

Tnx

are you using 'root' as your main user account? You should create a user for yourself to use. Linux is not like windows, and strictly speaking you should not log in to an X window session as root at all! If you need to do something as root you can type su in a shell to get access as root. Anyway I'm glad it's worked out for you.