So it appears your clients are updating, but they are not reporting back to the ePO Server. This is very similar to what I've experienced on my end after I upgraded some of my ePO Agents to CMA 3.6.0.453. Those PCs that upgraded to CMA 3.6.0.453 no longer took any policy changes I made on the ePO Server and DAT updates also never appeared to be reported correctly.
Not sure if the condition I'm seeing is the same as what you have, but it can be an easy check to test on one of your PCs.
On one of your PCs, locate the Agent_PCNAME.log file. (Substitute PCNAME with one of the PCs not reporting correctly) On my PC, it was located at C:\Documents and Settings\All Users\Application Data\McAfee\Common Framework\Db.
See if that log file has any indication of a "SignIt Error -2147483640". (Leave out the double quotes when searching) When I was going through the logs on my PCs that were having these problems, this is what I found on my PC.
Doing a search on McAfee's web site came up with the following web page (KB article #5803947):
When I used the workaround suggested in that KB article on my client PCs and deleted the registry keys mentioned and restarted the service, the agents were able to communicate with my ePO Server and policies were able to be downloaded and applied successfully and DAT updates were reported successfully as well.
Let see if you have the same problem.