Did someone change the McAfee Agent policy for the machines in question that got converted to super agents? In the Agent policy there is a check box for convert agents to super agents, that might be your cause.
I have nearly the same issue, random eposa SA repositories. This is a case for McAfee Support. I worked with them on this but for me it took to much time to proceed with needed checks (gathering MER logs from remote workstations with users not willing to cooperate or not easily to contact). The workaround was to reinstall local agent on the affected workstation. I've just check my repository list and I have still 3 listed as eposa and this situation is stable for last few weeks. This is not related to any policy change on our side.
Strange thing is no change had been made by anyone to any policies it just started doing it at 6pm yesterday, so I thought it may have been linked to a new DAT. The EPOSA name created was the name of one of our users computer, so then I thought there might be some underlying DNS issue. Anyway I rebooted the server and the newly created super agent had disappeared and everything is normal again (I hope).
Thanks for your responses.