I'd like to stress that none of this should cause your code any problems. The somewhat eager initialization of types without static constructors was entirely legitimate according to the C# and CLR specs, and so the new lazy behaviour of .NET 4.0. If your code assumed that just calling a static method, or creating an instance, would trigger initialization, then that's your own fault to some extent. That doesn't stop it being an interesting change to spot though :)

A good FYI. It should remain the same in .NET 4.0 release...?