Hey all those guys having this prob I had this problem too but managed to solve it. After i 
installed "rh9.ymessenger-1.0.4-1.i386.rpm" it ran only once. Every time afterwards i 
received the message "Segmentation Fault".
I am a KDE user on RedHatLinux9. Also i prefer bash on GUI and always use Konsole to
start ymessenger. This is what i did to handle the prob. It worked with me. Try it & it might
work with you. 

1-> uninstall the ymessenger here is the command
    #rpm -e ymessenger
    Incase this command doesn't works for you or you are having 
    problem uninstalling it, just delete the "ymessenger" and 
    "ymessenger.local" files in /usr/bin and move to step2
    here is the command to do that
    #cd /usr/bin
    #rm ymessenger
    #rm ymessenger.local
2-> Delete the directory "ymessenger" in /opt
    use GUI to do that or Konsole. Here is the command
    #cd /opt
    #rm -r ymessenger
    keep pressing y to acknowledge the delete process
3-> Delete the hidden directory ".ymessenger" located at /root
    use GUI. Simply go to /root and from view check the "show hidden 
    files" option. select the directory and del it.
4-> Ok we are done. now install ymessenger again. Move to the 
    directory containing the .rpm. Here is the command to install on  
    Konsole
    #rpm -ihv rh9.ymessenger-1.0.4-1.i386.rpm
    if this fails to work try -Uhv instead of -ihv in above command
    #rpm -Uhv rh9.ymessenger-1.0.4-1.i386.rpm
5-> After the installation procedure, just type "ymessenger" and there 
    you go. type "ymessenger" any where as the shortcut for it's 
    binary file is added in /usr/bin. Just type "ymessenger" whereever
    you are and with a little luck you'll be enjoying chatting with 
    you friends. ENJOY !! 

                                                                                                        Muhammad Majid