Coredump created when executing SqlPlus & SqlLoader from crontab!

It all started after replacing our server Unix. Data was recovered from a backup don eon the old server.
We also have some cases of brutal shutdown of the server, without any obvious reason. I don't think it's connceted to the coredump. It's not the same time.

Execution of shell with following statement ended with a coredump:
echo exit | sqlplus girard/girard @sqls/cde_jour >! /dev/null
Execution of le 01-04-01 a 05:00
sqlplus: Segmentation violation -- Core dumped

Was executed from crontab
0 5 1 * * /bin/csh /u/oracle/ >/u/oracle/cde_jour.log

Statements after the sqlplus-command was NEVER executed!
The reason must be that the shell terminated in coredump at exit from SlqPlus!

Why does it work manually, but not when executed by crontab?
We also have problem with application using SqlLoader. Works when executed manual, but fails (not always) when executed by crontab.

System: Unix - SCO OpenServer(TM) Release 5
Version Oracle: Version:
Version SqlPlus: SQL*Plus: Release

Hoping for a quick answer!