Recently I had the problem of ksh logins under HP-UX hanging. The symptom was that the login process would appear to work, all of the system profile and the user’s profile would be executed, then the login would hang.
This happened in Korn shell (ksh), but not the default POSIX shell (sh).
Turns out this is a FAQ (!) even though it’s something I’ve not run into these many years. In the comp.sys.hp.hpux faq it is question and answer 8.7. The answer to both symptoms is the fact that the history file ($HOME/.sh_history) is on an NFS mount. In the book Optimizing NFS Performance: Tuning and Troubleshooting NFS on HP-UX Systems (by Dave Olker) he discusses (in section 6.4: Avoiding NFS File Lock Hangs in Your Environment) how NFS locks can cause hangs such as the Korn shell hanging. A small portion of section 6.4 can be read online.
This also was discussed in this message thread on a LDAP mailing list. Turns out that the Korn shell was hanging as it was trying to open the history file ($LOGNAME/.sh_history). To fix the problem, move the history file to /tmp or some other local directory. One suggestion was /tmp/.sh_history.$$; there is probably a better idea which is more secure.
One solution was to make the NFS-mounted file mode 777; but this is definitely insecure and not a good idea.