leandroprz on "[Plugin: Google XML Sitemaps] Missing XML tag error on Google Webmaster Tools"

I updated to 4.0.2 and deleted the sitemap file by FTP as suggested here. I resubmitted the sitemap on Google Webmaster Tools and everything worked fine. But today I checked my site there and found this error.

These are the links on that screenshot:
http://leandroperez.com.ar/sitemap-pt-ds-gallery-2013-05.xml
http://leandroperez.com.ar/sitemap-pt-ds-gallery-2013-02.xml

How can I fix this?

Thanks

https://wordpress.org/plugins/google-sitemap-generator/