What is causing our LISTENER service to stop?

Here is the output from the lsnrctl status followed by the contents of listener.ora

sc9shrproddb01_PRDORA01:/usr/orasys/10.2.0.4/network/log $lsnrctl status

LSNRCTL for Linux: Version 10.2.0.4.0 - Production on 15-SEP-2012 18:15:49

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Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=10.x.xx.xx)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 10.2.0.4.0 - Production
Start Date                15-SEP-2012 16:31:49
Uptime                    0 days 1 hr. 43 min. 59 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /usr/orasys/10.2.0.4/network/admin/listener.ora
Listener Log File         /usr/orasys/10.2.0.4/network/log/listener.log
Listening Endpoints Summary...