error while connecting in spite of a valid connect string and a valid username/password

For some Unix account (not all) while starting the session, I have the message "host Hasn't answered for 15 seconds".
Yet I already succeeded in connecting with these accounts and I always can connect with an other emulator.
It seems that the trouble appeared after I made a "su -" to the account and the system asked me to change the password. Even if I restored the original password that WinScp understood it doesn't work. I asked Unix administrator to restart Unix account password but it doesn't work.
Can you help me

Try to specify /bin/bash shell on Shell tab of login dialog.