Before installing try if changing the permissions of the folder \"js\" and the file \"js/proxy.php\" to 755 fixes the problem.
The fix to remove the proxying method was mentioned here: http://www.magentocommerce.com/boards/viewthread/4679/P30/#t17628 by Scend
This should hopefully be only a temporary solution while Varien works on fixing this issue permanently. Once an official fix has been released this module would become obsolete. To install you need to manually go to the Downloader: http://your.magento.install.com/magento/downloader/ After installation you might need to delete the contents of your cache under /var/cache.