Since my prior post when I announced I've gone IPv6, I've had some time to setup all my client PCs. Well, try to anyway. It seems that in Mac OS X 10.5.6 (and likely a good bit prior), when you're attempting to statically assign an IPv6 address to an interface via the Network preferences GUI, it will appear all fine and good but not actually apply it.

In fact, it will strip the interface of any IPv6 address. Leaving you cold and shivering. Changing it to get its address automatically will work just fine either by router advertisements or using a self-assigned address, but that's the extent of System Preferences' help. I haven't seen this as a widely reported problem but I get the same situation on both my Mac Pro and MacBook Pro, wired or wireless.

I suspect that some piece of software might be interfering, but I've uninstalled VMWare and Tunnelblick with no change in behavior. Going to keep searching for an answer but if it really is a bug, probably isn't much I can do aside from contact Apple support.