js/lib/flex.js:425

----
return Flex.checkFlashPlayerVersion(major, minor, revision);

+++
try {
    return Flex.checkFlashPlayerVersion(major, minor, revision);
} catch (e) {
    console.log('This browser doesn\'t support Flash, or disables it by default.');
    return 0;
}

=================================
(only if "Uncaught TypeError: Cannot read property 'get' of undefined")

app/design/adminhtml/default/default/template/catalog/product/js.phtml:41

---
Event.observe($('tax_class_id'), 'change', recalculateTax);

+++
if ($('tax_class_id')) {
  Event.observe($('tax_class_id'), 'change', recalculateTax);
}