I am a big fan of EntitySpaces, a .NET ORM framework that I find very easy to use. When the developers upgraded the framework in 2010, they “broke” some things I used in my code. Specifically, they changed the way instantiate a new ORM entity. Entities used to have a method that looked like this…

esEntity.AddNew()

According to the release notes:
This method has been removed. It was optional in 2009 and has finally been removed. If you have overloaded or overridden this virtual method in a Custom class, you should move that logic to the constructor in your Custom classes (see above) and remove the custom AddNew method.

In fact, there were a bunch of “breaking” changes in ES2010. Keep a copy of the release notes when you upgrade past 2010 so that you will have a way to troubleshoot old apps when you upgrade them. (This is a good idea for all developer tools and languages, in fact.)