Importing 4.6 Asset ruined my 5.0 project

Hi

I have imported the immediate window editor extension to Unity 5. It is a 4.6 asset so I thought I would give it a go.

The immediate window is working fine, but it has somehow tempered with my project's settings. Namely I can no longer build my project. Error:

 UnauthorizedAccessException: Access to the path "Library\UnityAssemblies\UnityEngine.xml" is denied.
 System.IO.File.Delete (System.String path) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.IO/File.cs:179)
 SyntaxTree.VisualStudio.Unity.Bridge.Project.SafeDelete (System.String file)
 SyntaxTree.VisualStudio.Unity.Bridge.ProjectFilesGenerator.CleanDeployPath ()
 SyntaxTree.VisualStudio.Unity.Bridge.ProjectFilesGenerator.DeployUnityAssemblies (SyntaxTree.VisualStudio.Unity.Bridge.ProjectSystem.UnitySolution solution)
 SyntaxTree.VisualStudio.Unity.Bridge.ProjectFilesGenerator.GenerateProject ()
 SyntaxTree.VisualStudio.Unity.Bridge.Project+<>c__DisplayClass3.<RunOnceOnUpdate>b__2 ()
 UnityEditor.EditorApplication.Internal_CallUpdateFunctions () (at C:/buildslave/unity/build/artifacts/generated/common/editor/EditorApplication.gen.cs:268)

How can I go back to a normal functioning state?