[Sunhelp] SU: No shell problem

[Tuan Ba Dang]

Hello,

Please help me with this problem. My sparc 10 was running Sol 2.6
with no problem until last week, when I tried unsuccessfully to install 
PostOffice 3. Then the problem began, the system does not allow
any users except root log in anymore. After the user ID and passwd
are entered, the system thinks for a while then return to the login prompt.

Once log in as root, "su - userid" returns with:
SU: No shell

The /etc/passwd was untouched. All the shells are valid with
/usr/bin/ksh and /bin/sh.

Thanks in advance,
Tuan