How can I prevent the error "Unable to read the project file ... The attribute "xmlns" in element is unrecognized" when my Unity project reloads in Visual Studio 2010? I know how to temporarily fix this issue by editing the project's corresponding xml file and deleting out that offending attribute, but it's really annoying to have to keep doing this every time my project reloads. Here's a screenshot of the error: Some details: I'm using Unity Pro 4.1.1f4 on a Windows 7 machine and Visual Studio 2010 Professional. I never had this problem until I switched my External Editor setting in Unity to MonoDevelop for debugging, and then switched back to Visual Studio. Here's the node I have to remove/edit: Code (csharp): <ProjectExtensions xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <MonoDevelop> <Properties> <Policies> <TextStylePolicy EolMarker="Windows" inheritsSet="Mono" inheritsScope="text/plain" scope="text/x-csharp" /> <CSharpFormattingPolicy inheritsSet="Mono" inheritsScope="text/x-csharp" scope="text/x-csharp" /> </Policies> </Properties> </MonoDevelop> </ProjectExtensions> I've looked for posts about this error for a long time and I'm coming up empty. Thanks!