Just identified one more interesting bit of behaviour.
If I run CMDAGENT /S to show the Agent Status Monitor, then the McAfee Agent tray icon appears and the SideBySide errors stop completely.
However on logging off and back in, the issue reappears and the tray icon does not load and the SideBySide errors are reported again every 5 minutes.
Again running CMDAGENT /S resolves the issue until the next log off or restart.
I guess the workaround for now is to run CMDAGENT /S during the login but a permanent fix would be useful
I've noticed since above that the SideBySide error can be trigured by other events as well as CMDAGENT.
It now looks like the problem may be with a MS update (KB2507938 ) requiring reboot of server:
Will post if it resolves the issue.
I was having the same problem and uninstalled KB2507938, rebooted server and errors have stopped on the ePO server and no longer getting agent connection errors from my workstations.
A poster to the technet forum discussion referred to above says that MS11-063, released on August's Patch Tuesday, fixes the problem.
Can someone experiencing this problem test this and report back here?