login/exit problems

We have an Oracle 7.3.4 database that has been stable for a number of years but has started having problems during logon and exit with both sqlplus and remote logins. It hangs for up to a minute before connecting to Oracle server after you get

$ sqlplus ***/***

SQL*Plus: Release 3.3.4.0.1 - Production on Tue Jan 8 19:06:28 2002

Copyright (c) Oracle Corporation 1979, 1996. All rights reserved.

<hangs here>

and similarly following an exit from Oracle server after disconnecting

Disconnected from Oracle7 Server Release 7.3.4.0.1 - Production With the distributed, replication, parallel query and Spatial Data options PL/SQL Release 2.3.4.0.0 - Production

<hangs here>

before returning to OS command line prompt

lsnrctl, tnsping, etc suggest port is okay. Stopping and restarting database make no difference. Any advice or help will be much appreciated.

Tony

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