This is one that’s cropped up more than once, so for my own reference I’m sticking it up here as a post.

Situation is that an Exchange 2007 distribution group has the ‘Managed By’ field set to a certain user. That user however is unable to manage the group membership as the setting may imply. When attempting to do so they receive the message

Changes to the distribution list membership cannot be saved. You do not have sufficient permission to perform this operation on this object.

This behaviour is by design. For details on granting the appropriate permissions check out this post…

http://www.howexchangeworks.com/2009/09/giving-user-enough-rights-to-manage.html