I should have mentioned that since we did change our target to .NET 4.5, to use .NET 4 you have to use a different web.config so you would have to copy the contents of the Web.net40.config file into Web.config to avoid errors working in VS. This is the same as when someone wants to use .NET 3.5, they have to use the Web.net35.config contents. The default Web.config is now targeting .NET 4.5.
I guess in addition to turning the corner on our target framework we are apparently turning the corner on VS support and 2010 probably isn't going to cut it going forward. You might be able to use the Express version of VS 2013 Update 2.