An AJAX HTTP error occurred.

Following the google rabbit got me here --> http://forum.civicrm.org/index.php/topic,19232.msg81688.html?PHPSESSID=l71jel91j127g6eb4g229el963#msg81688

For laughs, I disabled XCache on my MAMP server, and the error did indeed go away. To be replaced with An AJAX HTTP error occurred. HTTP Result Code: 200 Debugging information follows. Path: /batch?id=8&op=do StatusText: OK ResponseText: Fatal error: Cannot access empty property in /Users/me/Sites/site.local/sites/all/modules/feeds/plugins/FeedsProcessor.inc on line 504

Is this issue only occuring for those using MAMP?

The line indicated above is this block:

<?php
  public function setTargetElement(FeedsSource $source, $target_item, $target_element, $value) {
    switch ($target_element) {
      case 'url':
      case 'guid':
        $target_item->feeds_item->$target_element = $value;
        break;
      default:
        $target_item->$target_element = $value;
        break;
    }
  }
?>

After refreshing, Drupal set a whole bunch of messages stating, in various undefined offsets:
Notice: Undefined offset: 22 in FeedsExcelParser->getItems()
Additionally:
Notice: Undefined index: FeedsExcelParser in FeedsSource->getConfigFor() (line 577 of /Users/me/Sites/site.local/sites/all/modules/feeds/includes/FeedsSource.inc).
Deprecated function: Assigning the return value of new by reference is deprecated in _feeds_excel_include_libraries() (line 43 of /Users/me/Sites/site.local/sites/all/modules/feeds_excel/feeds_excel.module).

So, I guess, it seems as though things aren't getting passed properly. I imagine this might have something to do with a new version of Drupal core.