What could be the cause of this error? I checked that the MySQL user can create and drop tables.
Moodle 2.7.3 (Build: 20141110)
[Thu Feb 19 15:07:35 2015] [error] [client 10.10.10.156] Default exception handler: Tabelle "resource_old" existiert nicht Debug: \nError code: ddltablenotexist\n* line 585 of /lib/dml/moodle_database.php: dml_exception thrown\n* line 1775 of /lib/dml/moodle_database.php: call to moodle_database->where_clause()\n* line 76 of /mod/resource/backup/moodle2/backup_resource_activity_task.class.php: call to moodle_database->record_exists()\n* line ? of unknownfile: call to backup_resource_activity_task::encode_content_links()\n* line 125 of /backup/moodle2/backup_xml_transformer.class.php: call to call_user_func()\n* line 88 of /backup/moodle2/backup_xml_transformer.class.php: call to backup_xml_transformer->encode_absolute_links()\n* line 273 of /backup/util/xml/xml_writer.class.php: call to backup_xml_transformer->process()\n* line 211 of /backup/util/xml/xml_writer.class.php: call to xml_writer->text_content()\n* line 110 of /backup/util/structure/backup_structure_processor.class.php: call to xml_writer->full_tag()\n* line 38 of /backup/util/structure/backup_final_element.class.php: call to backup_structure_processor->process_final_element()\n* line 97 of /backup/util/structure/backup_nested_element.class.php: call to backup_final_element->process()\n* line 97 of /backup/util/plan/backup_structure_step.class.php: call to backup_nested_element->process()\n* line 181 of /backup/util/plan/base_task.class.php: call to backup_structure_step->execute()\n* line 177 of /backup/util/plan/base_plan.class.php: call to base_task->execute()\n* line 120 of /backup/util/plan/backup_plan.class.php: call to base_plan->execute()\n* line 320 of /backup/controller/backup_controller.class.php: call to backup_plan->execute()\n* line 111 of /backup/util/ui/backup_ui.class.php: call to backup_controller->execute_plan()\n* line 131 of /backup/backup.php: call to backup_ui->execute()\n, referer: http://moodleXX.example.com/backup/backup.php
[Thu Feb 19 15:07:35 2015] [error] [client 10.10.10.156] Potential coding error - existing temptables found when disposing database. Must be dropped!, referer: http://moodleXX.example.com/backup/backup.php
by Visvanath Ratnaweera.