the line linking to the schemas seems to be the root of the problem
but I know that that has to be there!
anyway, if you change the two files as such
in the sitemap.xml file
then it all seems to work fine, (as in the xml sheet is delivered as a 'user readable' way with a table with URLs).
I scanned through the Google documentation and it says that the link to the schema is necessary, but I'm a little confused as to why linking this schema seems to break the layout for regular users, or even why the link to the schema is necessary.
but since I'm at work I'll leave that for you to figure out.