From the Admin Console, I selected Groups. I created two groups and added members. When I go back to the Admin Console and Browse for Groups, the ones I created are not in the list so I can not add/remove members. I logged in to the web client admin to complete the task.
I assume you are using Alfresco 4.0.d and the Share client. If so, I cannot reproduce the problem. That doesn't mean it is user error, though. Can you log in to Alfresco Explorer and manage the groups successfully?