1. did you ,Check the permissions on the services.ora file.  

   $ ls -l $ORACLE_HOME/network/agent/services.ora

You might see something like this:

   -rw-rw----   1 oracle dba  

2.  Verify the Intelligent Agent process is started by the Oracle 
(or equivalent DBA user).  If the Agent is started by a non DBA user, the user 
may not have permissions to read the services.ora file.

3.  Stop the Intelligent Agent
4.  Logon as Oracle or equivalent DBA user
5.  Remove the services.ora file  (The file will be recreated automatically when
    the agent is restarted.)
6.  Start the Intelligent Agent

7. if the above procedure doesnt work, then
   either
	Relink the agent executables as the Oracle user: 

	$ lsnrctl dbsnmp_stop 
	$ cd $ORACLE_HOME/network/lib 
	$ make -f ins_oemagent.mk install 
	$ lsnrctl dbsnmp_start 
   or
	Multiple Intelligent Agents may be installed on the system and the wrong Agent
	is running.