upon upgrading from 2.0.1 to 2.1 files with uppercase extension (e.g. .JPG) started throwing exceptions. I later found the problem was with any file extension not in lower case (e.g. FTL). The content-type is null (never set). If sitemesh is set to not decorate any pages, the file/page is served fine, and the content-type is set corectly. The exception is:

Java.lang.NullPointerException
        at com.opensymphony.module.sitemesh.filter.PageResponseWrapper.getPage(PageResponseWrapper.java:281)
        at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:157)
        at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:59)
        at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
        at com.caucho.server.http.Invocation.service(Invocation.java:315)
        at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
        at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:246)
        at com.caucho.server.http.HttpRequest.handleConnection(HttpRequest.java:163)
        at com.caucho.server.TcpConnection.run(TcpConnection.java:139)
        at java.lang.Thread.run(Thread.java:552)