Build fails because of xml documentation error

I am trying to build a ASP.NET MVC 2 project that uses Lucene.Net. I make a standard build definition in TFS 2010. When I queue a new build, it fails on this error:

CSC: Error generating XML documentation file 'xxx\xxx\Lucene.Net.xml' ('Access is denied. ')

But in my project properties for Lucene, I don't have xml comments checked. How can I get this to build correctly? I don't care about xml document files!