Microsoft.Build.Exceptions.BuildAbortedException: Build was canceled. Failed to successfully launch or connect to a child MSBuild.exe process. Verify that the MSBuild.exe "C:\Windows\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe" launches successfully, and that it is loading the same microsoft.build.dll that the launching process loaded.
Sometimes my leg falls asleep, and sometimes you just need to restart VS2012.