SOLVED: XML error - sitemap not working

[Montimontt]

Hi!
I have a problem and no idea how to solve it or where it cam from.
A few weeks ago the XML Sitemap worked. Now I have an error, different depending of the browser I use.

Working Sitemap: https://www.medero.de/sitemap
Not working XML: https://www.medero.de/index.php?option=com_xmap&view=xml&tmpl=component&id=1

I deinstalled XMAP 2.2.1 and installed I again. Still not working.
I am using Joomla 2.5.7

I would be very happy if someone could helf me with this.

Regards,
Montimontt

EDIT: I solved the problem by setting "Compress XML" to "no".