unable to open .../WNdb/dict/index.adv

When I perform the following a couple of million times I get the error unable to open .../WNdb/dict/index.adv:

function isWord(text, cb) {
    wordnet.lookup(text, function(results) {
        cb(Array.isArray(results) && results.length > 0);
    });
}

Is there anything I can do to resolve this?