"XML Parsing Error: not well-formed"

I wonder what this means. I installed the module as normal, enabled it, along with the nodes and engines sub-modules, but when I try to view the xml site map, I get a very odd error report:

XML Parsing Error: not well-formed
Location: http://dev.wosbee.com/files/xmlsitemap/gss.xsl
Line Number 1, Column 1:/modules/xmls/modules/xmlsitemap/gss/gss.jsp/gss/gss.css
^

The path it refers to in the last line is especially weird, as it doesn't resemble at all the paths of any of the files involved.