What is Utility_DSN? I'm not exactly sure when it happened, but I've started noticing that some of the hosts in my Enterprise Manager grid have a target named UTILITY_DSN. Does anyone know what this is? The one I noticed today appeared after reinstalling the agent. It shows as a datatbase instance, but with a non-existent Oracle Home.
I know this is a very late answer, but I've only just seen the question. The name of the target and the circumstances under which it appears suggest to me that you are using heterogenous services (or one of the database specific gateway products) in order to connect to a non-oracle database. The configuration of these links requires the creation of a service in the listener.ora on the database server (amongst other things). When an agent attempts to discover databases on a host it follows the following rules. 


parse /etc/oratab for databases listed there
parse $ORACLE_HOME/network/admin/listener.ora for statically registered databases
query the listener via lsnrctl to obtain service names. 


Stage 2 of this process will pick up any non-oracle targets defined in listener.ora. You probably want to delete them.