For Rice RHN-controlled RHEL5 hosts, the easiest way to install the Zabbix agent is through the EPEL RPM.
RHN has zabbix_agentd Version 1.4.7 which has many problems with Zabbix 1.8.3 on monitor.
You should install instead zabbix_agentd 1.8.x
If you haven't already added EPEL (Extra Packages for Enterprise Linux) you should start with:
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