AtomPub: wp-app.php failing APE

Hi there. I have a blog at http://blog.instantvoodoomagic.com. If I pass http://blog.instantvoodoomagic.com/wp-app.php to APE (http://www.tbray.org/ape/), it tells me that if failed because “HTTP/1.1 Credentials required”. However, if I type http://blog.instantvoodoomagic.com/wp-app.php into Safari, it downloads an atom.xml file just fine. If I then type the same URL into Camino (which runs the Gecko engine), it tells me “401 Unauthorized”.

Can anyone tell me what’s going on here? Shouldn’t Safari also return 401 unauthorized?

If it makes any difference, I am hosting at mediatemple.