I set my services to use the domain account I had created for epo and this then worked a treat. Local System did not.
Did you select to force the agent instalation to install over existing agents?
Please check if the push actually succeeded to these machines (epoapsvr.log) should contain the details of the push. If there are no errors during push, the frminst_<machinename>.log would contain the details of the installation (the actual install is logged in mfeagentmsi.log).
Also, whats the version of the agent on the client and version are you pushing?