Any update on this Joe?
Have you thought of posting a tracker item.
I can find this: https://tracker.moodle.org/browse/MDL-31015 that claims to be fixed, and is NOT quite the same.
Our case: Moodle 2.4.3+ (Build: 20130405)
Works: http://en.wikipedia.org/wiki/List_of_DNS_record_types and a lot of wikipedia
No work: http://gpg4win.org/ - intermediate page
Inconsistent and unpredicatable behaviour with URL resource. Cannot find a reason.
-Derek