Let's try altering this a bit to use readystate checks (untested):

```javascript
function ready( json ) {
   _readyCallback = _readyCallback || function(){};

  function domReady() {
    // If the DOM isn't ready yet, repeat when it is
    if ( document.readyState !== "complete" ) {
      document.onreadystatechange = domReady;
      return;
    }
    document.onreadystatechange = null;
    _strings = json;
    _isReady = true;
    _readyCallback();
  }

  domReady();    
}
```