Actually, the same thing happens with PostgreSQL:

2014-01-08 14:11:25 CET ERROR:  invalid input syntax for type timestamp: "" at character 4367
2014-01-08 14:11:25 CET STATEMENT:  SELECT anon_1.anon_2_images_created_at AS anon_1_anon_2_images_created_at, anon_1.anon_2_images_updated_at AS anon_1_anon_2_images_updated_at, anon_1.anon_2_images_deleted_at AS anon_1_anon_2_images_deleted_at, anon_1.anon_2_images_deleted AS anon_1_anon_2_images_deleted, anon_1.anon_2_images_id AS anon_1_anon_2_images_id, anon_1.anon_2_images_name AS anon_1_anon_2_images_name, anon_1.anon_2_images_disk_format AS anon_1_anon_2_images_disk_format, anon_1.anon_2_images_container_format AS anon_1_anon_2_images_container_format, anon_1.anon_2_images_size AS anon_1_anon_2_images_size, anon_1.anon_2_images_status AS anon_1_anon_2_images_status, anon_1.anon_2_images_is_public AS anon_1_anon_2_images_is_public, anon_1.anon_2_images_checksum AS anon_1_anon_2_images_checksum, anon_1.anon_2_images_min_disk AS anon_1_anon_2_images_min_disk, anon_1.anon_2_images_min_ram AS anon_1_anon_2_images_min_ram, anon_1.anon_2_images_owner AS anon_1_anon_2_images_owner, anon_1.anon_2_images_protected AS anon_1_anon_2_images_protected, image_locations_1.created_at AS image_locations_1_created_at, image_locations_1.updated_at AS image_locations_1_updated_at, image_locations_1.deleted_at AS image_locations_1_deleted_at, image_locations_1.deleted AS image_locations_1_deleted, image_locations_1.id AS image_locations_1_id, image_locations_1.image_id AS image_locations_1_image_id, image_locations_1.value AS image_locations_1_value, image_locations_1.meta_data AS image_locations_1_meta_data, image_properties_1.created_at AS image_properties_1_created_at, image_properties_1.updated_at AS image_properties_1_updated_at, image_properties_1.deleted_at AS image_properties_1_deleted_at, image_properties_1.deleted AS image_properties_1_deleted, image_properties_1.id AS image_properties_1_id, image_properties_1.image_id AS image_properties_1_image_id, image_properties_1.name AS image_properties_1_name, image_properties_1.value AS image_properties_1_value
        FROM (SELECT anon_2.images_created_at AS anon_2_images_created_at, anon_2.images_updated_at AS anon_2_images_updated_at, anon_2.images_deleted_at AS anon_2_images_deleted_at, anon_2.images_deleted AS anon_2_images_deleted, anon_2.images_id AS anon_2_images_id, anon_2.images_name AS anon_2_images_name, anon_2.images_disk_format AS anon_2_images_disk_format, anon_2.images_container_format AS anon_2_images_container_format, anon_2.images_size AS anon_2_images_size, anon_2.images_status AS anon_2_images_status, anon_2.images_is_public AS anon_2_images_is_public, anon_2.images_checksum AS anon_2_images_checksum, anon_2.images_min_disk AS anon_2_images_min_disk, anon_2.images_min_ram AS anon_2_images_min_ram, anon_2.images_owner AS anon_2_images_owner, anon_2.images_protected AS anon_2_images_protected
        FROM (SELECT images.created_at AS images_created_at, images.updated_at AS images_updated_at, images.deleted_at AS images_deleted_at, images.deleted AS images_deleted, images.id AS images_id, images.name AS images_name, images.disk_format AS images_disk_format, images.container_format AS images_container_format, images.size AS images_size, images.status AS images_status, images.is_public AS images_is_public, images.checksum AS images_checksum, images.min_disk AS images_min_disk, images.min_ram AS images_min_ram, images.owner AS images_owner, images.protected AS images_protected
        FROM images                                                                                                                                                                                              
        WHERE images.is_public = true OR images.owner = '080b784baeea487587786b160e2f30b5' UNION SELECT images.created_at AS images_created_at, images.updated_at AS images_updated_at, images.deleted_at AS images_deleted_at, images.deleted AS images_deleted, images.id AS images_id, images.name AS images_name, images.disk_format AS images_disk_format, images.container_format AS images_container_format, images.size AS images_size, images.status AS images_status, images.is_public AS images_is_public, images.checksum AS images_checksum, images.min_disk AS images_min_disk, images.min_ram AS images_min_ram, images.owner AS images_owner, images.protected AS images_protected
        FROM images JOIN image_members ON images.id = image_members.image_id                                                                                                                                     
        WHERE image_members.deleted = false AND image_members.member = '080b784baeea487587786b160e2f30b5') AS anon_2
        WHERE anon_2.images_deleted = false AND anon_2.images_status != 'killed' AND (CASE WHEN (anon_2.images_created_at IS NOT NULL) THEN anon_2.images_created_at ELSE '' END < '2013-10-01T11:33:53.563480'::timestamp OR CASE WHEN (anon_2.images_created_at IS NOT NULL) THEN anon_2.images_created_at ELSE '' END = '2013-10-01T11:33:53.563480'::timestamp AND CASE WHEN (anon_2.images_id IS NOT NULL) THEN anon_2.images_id ELSE '' END < '1166c6a9-c4b9-48e4-b529-fd3923d68a6e') ORDER BY anon_2.images_created_at DESC, anon_2.images_id DESC
         LIMIT 20) AS anon_1 LEFT OUTER JOIN image_locations AS image_locations_1 ON anon_1.anon_2_images_id = image_locations_1.image_id LEFT OUTER JOIN image_properties AS image_properties_1 ON anon_1.anon_2_images_id = image_properties_1.image_id ORDER BY anon_1.anon_2_images_created_at DESC, anon_1.anon_2_images_id DESC