With the releases of RC1s for IE, .NET 3.0 and Vista, there has been a slight change in CardSpace. The http://schemas.microsoft.com/ws/2005/05/identity namespace has been discontinued in favor of http://schemas.xmlsoap.org/ws/2005/05/identity. In accordance with this change, as of today, the Infocard usage within my site has been updated to use the new namespace. Anyone running an older implementation will most likely be greeted with a message stating that the site requires a managed card.
This message is not really true and just means anyone using older CardSpace cannot access the site until they upgrade. I use the namespace when calling CardSpace only to identity the claims I require when submitting a card. The good news is that this change was only comsetic, requiring the small change on the registration and login forms. No backend code changes were required to support this namespace change.
Warning: I upgraded both my .Net 3.0 framework and IE 7 one after another and never backed up my previously created cards. Once my system was up and running and I launched the Windows CardSpace, I was greeted by a nice message telling me that either my cards were corrupted or somehow were removed from the system. I did not have a backup of them (good thing I have only been playing around with them so far) and was required to re-create my cards and re-establish relationships with sites using my cards again.
Lesson learned: Backup your cards prior to upgrading if you dont want to lose them!