Error message

• Warning: Cannot modify header information - headers already sent by (output started at /usr/share/drupal7/includes/common.inc:2800) in drupal_send_headers() (line 1499 of /usr/share/drupal7/includes/bootstrap.inc).
• Error: Class 'FeedsHTTPCache' not found in feeds_cron() (line 82 of /usr/share/drupal7/modules/feeds/feeds.module).