I had an alert that triggered when a trait changed (in my case, the alert was on RHQ Agent resource, when the SIGAR version trait changed).

When the alert triggers, you cannot see the alert data because the alert data source is trying to convert the trait string (which is probably not a raw number) to a Double:

java.lang.NumberFormatException:For input string: "Version=1.6.5.132 (05/20/2010 04:04 AM); Native version=1.6.5.132 (05/20/2010 04:04 AM)"
--- STACK TRACE FOLLOWS ---
For input string: "Version=1.6.5.132 (05/20/2010 04:04 AM); Native version=1.6.5.132 (05/20/2010 04:04 AM)"
    at Unknown.com_google_gwt_core_client_impl_StackTraceCreator$CollectorMoz_collect__Lcom_google_gwt_core_client_JsArrayString_2(Unknown source:0)
    at Unknown.com_google_gwt_core_client_impl_StackTraceCreator_createStackTrace__Lcom_google_gwt_core_client_JsArrayString_2(Unknown source:0)
    at Unknown.com_google_gwt_core_client_impl_StackTraceCreator$Collector_fillInStackTrace__Ljava_lang_Throwable_2V(Unknown source:0)
    at Unknown.com_google_gwt_core_client_impl_StackTraceCreator_fillInStackTrace__Ljava_lang_Throwable_2V(Unknown source:0)
    at Unknown.java_lang_Throwable_fillInStackTrace__Ljava_lang_Throwable_2(Unknown source:0)
    at Unknown.java_lang_Throwable_$$init__Ljava_lang_Throwable_2V(Unknown source:0)
    at Unknown.java_lang_Throwable_$Throwable__Ljava_lang_Throwable_2Ljava_lang_String_2Ljava_lang_Throwable_2(Unknown source:0)
    at Unknown.java_lang_Exception_$Exception__Ljava_lang_Exception_2Ljava_lang_String_2Ljava_lang_Exception_2(Unknown source:0)
    at Unknown.java_lang_RuntimeException_$RuntimeException__Ljava_lang_RuntimeException_2Ljava_lang_String_2Ljava_lang_RuntimeException_2(Unknown source:0)
    at Unknown.java_lang_IllegalArgumentException_$IllegalArgumentException__Ljava_lang_IllegalArgumentException_2Ljava_lang_String_2Ljava_lang_IllegalArgumentException_2(Unknown source:0)
    at Unknown.java_lang_NumberFormatException_$NumberFormatException__Ljava_lang_NumberFormatException_2Ljava_lang_String_2Ljava_lang_NumberFormatException_2(Unknown source:0)
    at Unknown.java_lang_NumberFormatException_forInputString__Ljava_lang_String_2Ljava_lang_NumberFormatException_2(Unknown source:0)
    at Unknown.java_lang_Number__1_1parseAndValidateDouble__Ljava_lang_String_2D(Unknown source:0)
    at Unknown.java_lang_Double_parseDouble__Ljava_lang_String_2D(Unknown source:0)
    at Unknown.java_lang_Double_valueOf__Ljava_lang_String_2Ljava_lang_Double_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource_convert__Lorg_rhq_core_domain_alert_Alert_2Lcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource_$copyValues__Lorg_rhq_enterprise_gui_coregui_client_alert_AlertDataSource_2Lorg_rhq_core_domain_alert_Alert_2Lcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource_copyValues__Ljava_lang_Object_2Lcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_util_RPCDataSource_copyValues__Ljava_lang_Object_2ZLcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_util_RPCDataSource_$buildRecords__Lorg_rhq_enterprise_gui_coregui_client_util_RPCDataSource_2Ljava_util_Collection_2Z_3Lcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_util_RPCDataSource_$buildRecords__Lorg_rhq_enterprise_gui_coregui_client_util_RPCDataSource_2Ljava_util_Collection_2_3Lcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_util_RPCDataSource_buildRecords__Ljava_util_Collection_2_3Lcom_smartgwt_client_widgets_grid_ListGridRecord_2(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource$8_onTypesLoaded__Ljava_util_Map_2V(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_inventory_resource_type_ResourceTypeRepository_$getResourceTypes__Lorg_rhq_enterprise_gui_coregui_client_inventory_resource_type_ResourceTypeRepository_2_3Ljava_lang_Integer_2Ljava_util_EnumSet_2Lorg_rhq_enterprise_gui_coregui_client_inventory_resource_type_ResourceTypeRepository$TypesLoadedCallback_2V(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_inventory_resource_type_ResourceTypeRepository_$getResourceTypes__Lorg_rhq_enterprise_gui_coregui_client_inventory_resource_type_ResourceTypeRepository_2_3Ljava_lang_Integer_2Lorg_rhq_enterprise_gui_coregui_client_inventory_resource_type_ResourceTypeRepository$TypesLoadedCallback_2V(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource_$dataRetrieved__Lorg_rhq_enterprise_gui_coregui_client_alert_AlertDataSource_2Lorg_rhq_core_domain_util_PageList_2Lcom_smartgwt_client_data_DSResponse_2Lcom_smartgwt_client_data_DSRequest_2V(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_dashboard_portlets_recent_alerts_AbstractRecentAlertsPortlet$AlertsPortletDataSource_dataRetrieved__Lorg_rhq_core_domain_util_PageList_2Lcom_smartgwt_client_data_DSResponse_2Lcom_smartgwt_client_data_DSRequest_2V(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource$7_$onSuccess__Lorg_rhq_enterprise_gui_coregui_client_alert_AlertDataSource$7_2Lorg_rhq_core_domain_util_PageList_2V(Unknown source:0)
    at Unknown.org_rhq_enterprise_gui_coregui_client_alert_AlertDataSource$7_onSuccess__Ljava_lang_Object_2V(Unknown source:0)