please find server.log in the ePO install directory on the server and after enforcing an ASCI from the client's agent monitor, check what this log says about the connection. Look for the client's name in this log (entries may be scattered among other entries, not getting displayed contiguously).
To enforce ASC (agent to server communication) from the client, right-click the McAfee Icon in the system tray on the client and select McAfee Agent Status Monitor (assuming MA 4.5).
Then hit the 'collect & send' button.
As an aside - for a rapid learning experience about ePO there's a whole bunch of instructional video's on the McAfee Service Portal website.
Well worth a look.