When I try to view an attached .doc file I get an exception:

javax.servlet.ServletException: failed to handle GET request
com.zimbra.cs.extension.ExtensionDispatcherServlet .service(ExtensionDispatcherServlet.java:111)
javax.servlet.http.HttpServlet.service(HttpServlet .java:802)
com.zimbra.cs.service.formatter.NativeFormatter.ha ndleMessagePart(NativeFormatter.java:140)
com.zimbra.cs.service.formatter.NativeFormatter.ha ndleMessage(NativeFormatter.java:99)
com.zimbra.cs.service.formatter.NativeFormatter.fo rmatCallback(NativeFormatter.java:83)
com.zimbra.cs.service.formatter.Formatter$FormatOp eration.callback(Formatter.java:246)
com.zimbra.cs.operation.Operation.schedule(Operati on.java:190)
com.zimbra.cs.service.formatter.Formatter.format(F ormatter.java:88)
com.zimbra.cs.service.UserServlet.doAuthGet(UserSe rvlet.java:388)
com.zimbra.cs.service.UserServlet.doGet(UserServle t.java:290)
javax.servlet.http.HttpServlet.service(HttpServlet .java:689)
com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:173)
javax.servlet.http.HttpServlet.service(HttpServlet .java:802)

root cause

com.zimbra.cs.service.ServiceException: system failure: Extension HTTP handler not found at /convertd
com.zimbra.cs.service.ServiceException.FAILURE(Ser viceException.java:174)
com.zimbra.cs.extension.ExtensionDispatcherServlet .getHandler(ExtensionDispatcherServlet.java:146)
com.zimbra.cs.extension.ExtensionDispatcherServlet .service(ExtensionDispatcherServlet.java:99)
javax.servlet.http.HttpServlet.service(HttpServlet .java:802)
com.zimbra.cs.service.formatter.NativeFormatter.ha ndleMessagePart(NativeFormatter.java:140)
com.zimbra.cs.service.formatter.NativeFormatter.ha ndleMessage(NativeFormatter.java:99)
com.zimbra.cs.service.formatter.NativeFormatter.fo rmatCallback(NativeFormatter.java:83)
com.zimbra.cs.service.formatter.Formatter$FormatOp eration.callback(Formatter.java:246)
com.zimbra.cs.operation.Operation.schedule(Operati on.java:190)
com.zimbra.cs.service.formatter.Formatter.format(F ormatter.java:88)
com.zimbra.cs.service.UserServlet.doAuthGet(UserSe rvlet.java:388)
com.zimbra.cs.service.UserServlet.doGet(UserServle t.java:290)
javax.servlet.http.HttpServlet.service(HttpServlet .java:689)
com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:173)
javax.servlet.http.HttpServlet.service(HttpServlet .java:802)

What have I missed?

MacOSX PPC 10.4.7
ZCS 4.0.0 GA 303