Error in POST for Obs resource

echo '
{
"person":{"uuid":"707ed494-22fe-43cd-9751-0c39242b741b"},
"obsDatetime":"2012-09-19T00:00:00.000+0530",
"concept":{"uuid":"2f098028-153a-4f30-bcef-bd62fa01255b"},
"location":{"uuid":"8d6c993e-c2cc-11de-8d13-0010c6dffd0f"},
"encounter":{"uuid":"e585bd32-3e43-4391-81b7-9ff575225671"},
"value":"no problem"
}
' | curl -i -H "Content-type: application/json" -X POST -d @- https://localhost:8443/openmrs/ws/rest/v1/obs -k -b cookies.txt -3

{"error":{"message":"Unable to convert object into response content","code":"org.openmrs.module.webservices.rest.web.resource.impl.BaseDelegatingResource:685","detail":"org.openmrs.module.webservices.rest.web.response.ConversionException: concept on class org.openmrs.Obs\n\tat org.openmrs.module.webservices.rest.web.resource.impl.BaseDelegatingResource.setProperty(BaseDelegatingResource.java:685)\n\tat org.openmrs.module.webservices.rest.web.resource.impl.BaseDelegatingResource.setConvertedProperties(BaseDelegatingResource.java:543)\n\tat org.openmrs.module.webservices.rest.web.resource.impl.DelegatingCrudResource.create(DelegatingCrudResource.java:90)\n\tat org.openmrs.module.webservices.rest.web.v1_0.controller.BaseCrudController.create(BaseCrudController.java:83)\n\tat sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)\n\tat sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)\n\tat sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)\n\tat java.lang.reflect.Method.invoke(Method.java:616)\n\tat org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)\n\tat org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)\n\tat org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)\n\tat org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)\n\tat org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)\n\tat org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)\n\tat org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)\n\tat javax.servlet.http.HttpServlet.service(HttpServlet.java:637)\n\tat javax.servlet.http.HttpServlet.service(HttpServlet.java:717)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.openmrs.module.web.filter.ForcePasswordChangeFilter.doFilter(ForcePasswordChangeFilter.java:65)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.openmrs.module.web.filter.ModuleFilterChain.doFilter(ModuleFilterChain.java:76)\n\tat org.openmrs.module.webservices.rest.web.filter.AuthorizationFilter.doFilter(AuthorizationFilter.java:100)\n\tat org.openmrs.module.web.filter.ModuleFilterChain.doFilter(ModuleFilterChain.java:74)\n\tat org.springframework.web.filter.ShallowEtagHeaderFilter.doFilterInternal(ShallowEtagHeaderFilter.java:58)\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)\n\tat org.openmrs.module.web.filter.ModuleFilterChain.doFilter(ModuleFilterChain.java:74)\n\tat org.openmrs.module.web.filter.ModuleFilter.doFilter(ModuleFilter.java:58)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.openmrs.web.filter.OpenmrsFilter.doFilterInternal(OpenmrsFilter.java:111)\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.openmrs.web.filter.StartupFilter.doFilter(StartupFilter.java:109)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.openmrs.web.filter.StartupFilter.doFilter(StartupFilter.java:109)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.openmrs.web.filter.StartupFilter.doFilter(StartupFilter.java:109)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)\n\tat org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)\n\tat org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)\n\tat org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)\n\tat org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)\n\tat org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)\n\tat org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)\n\tat org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)\n\tat org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)\n\tat org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)\n\tat org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)\n\tat org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)\n\tat org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)\n\tat java.lang.Thread.run(Thread.java:679)\nCaused by: java.lang.reflect.InvocationTargetException\n\tat sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)\n\tat sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)\n\tat sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)\n\tat java.lang.reflect.Method.invoke(Method.java:616)\n\tat org.openmrs.module.webservices.rest.web.resource.impl.BaseDelegatingResource.setProperty(BaseDelegatingResource.java:655)\n\t... 61 more\nCaused by: java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to java.lang.String\n\tat org.openmrs.module.webservices.rest.web.v1_0.resource.ObsResource.setConcept(ObsResource.java:253)\n\t... 66 more\n"}}