HTTP error on sitemap status

I have submitted the following sitemaps to Google, only the last one is
being retrieved properly (the gz is simply a compressed version of the
.xml file, the later of which will go away once I get this working).

http://www.southernapartments.com/sitemapauto.xml
http://www.southernapartments.com/sitemap.gz
http://www.modellocate.com/sitemapauto.xml
http://www.modellocate.com/sitemap.gz

The Google report just says "HTTP error" but is so vague I have no idea
what the failure is. I see nothing out of the ordinary in my server
logs and I can retrieve the file directly with IE, Firefox, and even
wget from a remote linux box.

Anyone have a clue?

TIA,
Lance
Charleston Software Associates