Infite SEO sitemap error

Hi there!
Infinite SEO autogenerate sitemap for each of my blog installation on my network, but that sitemap don't work. I get the message
This page contains the following errors:
error on line 3 at column 6: XML declaration allowed only at the start of the document

how can I solve this?

than I would like to ask:
- the blogs of my network are in constantly updating, does the sitemap will be update sometimes?

- Google webmaster tools give me the possibility to post a sitemap. Since I have a sitemap for each blog, should I post all the sitemap I have?