Error: Expected patient family name

ERROR - XformsQueueProcessor.submitXForm(297) |2012-03-14 12:32:06,017| Expected patient family name value
java.lang.Exception: Expected patient family name value
        at org.openmrs.module.xforms.XformsQueueProcessor.fillPatientIdIfMissing(XformsQueueProcessor.java:786)
        at org.openmrs.module.xforms.XformsQueueProcessor.submitXForm(XformsQueueProcessor.java:280)
        at org.openmrs.module.xforms.XformsQueueProcessor.processXForm(XformsQueueProcessor.java:177)
        at org.openmrs.module.xforms.download.XformDataUploadManager.queueForm(XformDataUploadManager.java:227)
        at org.openmrs.module.xforms.download.XformDataUploadManager.submitXforms(XformDataUploadManager.java:76)
        at org.openmrs.module.xforms.XformsServer.submitXforms(XformsServer.java:188)
        at org.openmrs.module.xforms.XformsServer.processConnection(XformsServer.java:122)
        at org.openmrs.module.xforms.web.UserDownloadServlet.doGet(UserDownloadServlet.java:43)
        at org.openmrs.module.xforms.web.UserDownloadServlet.doPost(UserDownloadServlet.java:37)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.openmrs.module.web.ModuleServlet.service(ModuleServlet.java:72)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.openmrs.module.web.filter.ForcePasswordChangeFilter.doFilter(ForcePasswordChangeFilter.java:65)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.openmrs.module.web.filter.ModuleFilterChain.doFilter(ModuleFilterChain.java:76)
        at org.openmrs.module.xforms.web.XformsFilter.doFilter(XformsFilter.java:60)
        at org.openmrs.module.web.filter.ModuleFilterChain.doFilter(ModuleFilterChain.java:74)
        at org.openmrs.module.web.filter.ModuleFilter.doFilter(ModuleFilter.java:58)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.openmrs.web.filter.OpenmrsFilter.doFilterInternal(OpenmrsFilter.java:112)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.openmrs.web.filter.StartupFilter.doFilter(StartupFilter.java:83)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.openmrs.web.filter.StartupFilter.doFilter(StartupFilter.java:83)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.openmrs.web.filter.StartupFilter.doFilter(StartupFilter.java:83)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:574)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1527)
        at java.lang.Thread.run(Thread.java:619)