snmpd silently dies after being started

I installed snmpd on a machine running CentOS 4.5 using "yum install
net-snmp",
but whenever I start the snmpd service, it starts with
no error but then dies silently:

[root@localhost cacti]# service snmpd start
Starting snmpd: [ OK ]
[root@localhost cacti]# ps auwx | grep snmp
root 26756 0.0 0.0 4640 624 pts/0 S+ 02:25 0:00 grep
snmp
[root@localhost cacti]#

[i.e. "ps auwx | grep snmp" should list any instances of snmpd that
were
running, but none are listed]

What might be causing the snmpd daemon to fail? Does it write an
error log
anywhere when it winks out like that?
.