They are both wrong in opposite ways. Windows 7 releases its DHCPv6-assigned address the moment it gets an RA with Managed = 0, and Mac OS X ignores DHCPv6 even when Managed=1, and autoconfigures with SLAAC instead. Very strange! Details, screen shots, and a PCAP file here: http://samsclass.info/ipv6/proj/FlipFlop.html