Will not accept Context

Editing a feed that has been working on my site for months. When I tried to edit the settings for XPath XML parser, it would not save the changes. It complains about the Context, which is "//videos/video". In fact, I can't get it to accept any selector at all for Context, including examples from the XPath parser documentation. Exported importer is as follows:

$feeds_importer = new stdClass();
$feeds_importer->disabled = FALSE; /* Edit this to true to make a default feeds_importer disabled initially */
$feeds_importer->api_version = 1;
$feeds_importer->id = 'experimental_video_importer';
$feeds_importer->config = array(
  'name' => 'experimental video importer',
  'description' => '',
  'fetcher' => array(
    'plugin_key' => 'FeedsFileFetcher',
    'config' => array(
      'allowed_extensions' => 'txt csv tsv xml opml html htm',
      'direct' => 1,
      'directory' => 'public://feeds',
      'allowed_schemes' => array(
        0 => 'public',
      ),
    ),
  ),
  'parser' => array(
    'plugin_key' => 'FeedsXPathParserXML',
    'config' => array(
      'sources' => array(
        'xpathparser:0' => 'caption',
        'xpathparser:2' => 'id',
        'xpathparser:4' => 'gpslatitude',
        'xpathparser:5' => 'gpslongitude',
        'xpathparser:6' => 'useremail',
        'xpathparser:7' => 'url',
        'xpathparser:8' => 'id',
        'xpathparser:9' => 'path',
      ),
      'rawXML' => array(
        'xpathparser:0' => 0,
        'xpathparser:2' => 0,
        'xpathparser:4' => 0,
        'xpathparser:5' => 0,
        'xpathparser:6' => 0,
        'xpathparser:7' => 0,
        'xpathparser:8' => 0,
        'xpathparser:9' => 0,
      ),
      'context' => '//videos/video',
      'exp' => array(
        'errors' => 1,
        'debug' => array(
          'context' => 'context',
          'xpathparser:0' => 'xpathparser:0',
          'xpathparser:2' => 'xpathparser:2',
          'xpathparser:4' => 'xpathparser:4',
          'xpathparser:5' => 'xpathparser:5',
          'xpathparser:6' => 'xpathparser:6',
          'xpathparser:7' => 'xpathparser:7',
          'xpathparser:8' => 'xpathparser:8',
          'xpathparser:9' => 'xpathparser:9',
        ),
      ),
      'allow_override' => 0,
    ),
  ),
  'processor' => array(
    'plugin_key' => 'FeedsNodeProcessor',
    'config' => array(
      'expire' => '-1',
      'author' => 0,
      'authorize' => 1,
      'mappings' => array(
        0 => array(
          'source' => 'xpathparser:0',
          'target' => 'title',
          'unique' => FALSE,
        ),
        1 => array(
          'source' => 'xpathparser:2',
          'target' => 'guid',
          'unique' => 1,
        ),
        2 => array(
          'source' => 'xpathparser:4',
          'target' => 'field_location:locpick][user_latitude',
          'unique' => FALSE,
        ),
        3 => array(
          'source' => 'xpathparser:5',
          'target' => 'field_location:locpick][user_longitude',
          'unique' => FALSE,
        ),
        4 => array(
          'source' => 'xpathparser:6',
          'target' => 'user_mail',
          'unique' => FALSE,
        ),
        5 => array(
          'source' => 'xpathparser:7',
          'target' => 'path_alias',
          'unique' => FALSE,
        ),
        6 => array(
          'source' => 'xpathparser:8',
          'target' => 'field_staging_id',
          'unique' => FALSE,
        ),
        7 => array(
          'source' => 'xpathparser:9',
          'target' => 'field_video_file',
          'unique' => FALSE,
        ),
      ),
      'update_existing' => '0',
      'input_format' => 'plain_text',
      'skip_hash_check' => 0,
      'bundle' => 'video',
    ),
  ),
  'content_type' => 'video_feed',
  'update' => 0,
  'import_period' => '-1',
  'expire_period' => 3600,
  'import_on_create' => 0,
  'process_in_background' => 0,
);

Feed data looks like this:

<?xml version="1.0"?>
<videos>
<video>
<id>1234</id>
<caption>My Video</caption>
<gpslatitude>40</gpslatitude>
<gpslongitude>-78</gpslongitude>
<path>public://media/myvideo.mov</path>
<useremail>myemail@google.com</useremail>
</video>
</videos>