Smart groups that are based upon advanced search membership are broken after upgrade from 4.6.4 to 4.6.5. After the upgrade, the groups have everyone in the database. When you select contacts in group and then click on the edit smart group search criteria you get the advanced search form. The section for membership is expanded but the group is not selected nor is membership status filled in.
I can fix the groups but it's a bit of a pain.
I looked at the criteria in the civicrm_groups after the upgrade. It looks the same as before the upgrade and doesn't work. Once you manually fix them then the criteria is different. I'm not sure if the civicrm_membership_cache is messed up or if the criteria isn't getting update.