I installed sitemapXML to create my sitemaps and am getting 500 errors from Google.

I have five sitemaps in the Sitemap index.
/sitemapcategories.xml and /sitemapproducts.xml appear to be ok. All categories and products were submitted without issue.

The other three are showing 1 warning each. They are:

/sitemapezpages.xml
There are seven url's in this sitemap.and it is the first which i showing the error so I don't know if the others were indexed and ok or not indexed at all.
The url showing the error is URL: /index.php?main_page=page&id=3&chapter=10 which points to - This is "Another New Page" This is yet another new page or link that is part of Chapter 10.

What is chapter 10 ??? Can this page be safely removed, if so where do I remove it from?

/sitemapmainpage.xml
URL: /index.php?main_page=index This is the home page?? so I have no idea what is going on here.

/sitemapmanufacturers.xml
URL: /index.php?main_page=index&manufacturers_id=10 This goes to a page which says 'There are no products to list in this category'
This is the only url in this sitemap and as far as I can see, not needed.

What is the best way to approach this? Should I put some sort of exclude in .htaccess or is there another way?

Constructive help is always appreciated. Thanks.