It sounds like you’re not using the Game class and running everything within the game loop. The MG 3.2 changes seem to make the GraphicsDevice creation dependent on the Game class. Logically, it shouldn’t be, but I guess since most people use MG for making games, developers didn’t notice/care. Hopefully it will change in the future.
See this post: “It turns out that since version 3.2 create GraphicsDevice outside Game class is impossible frowning”