Error message

Warning: igbinary_unserialize_header: unsupported version: "pmen"..., should begin with a binary version header of "\x00\x00\x00\x01" or "\x00\x00\x00\x02" in _dmemcache_get_pieces() (line 340 of /mnt/www/html/txhhs/docroot/sites/all/modules/contrib/memcache/dmemcache.inc).