This is because those articles are posted with reference links. You need to check your website in Google Webmasters (If you have an account for your site) to ensure what exactly is the reason. Also check your site for the references Google has quoted. This will help in solving your problem. You can also read some posts related to Website Penalization and recovery methods.
Good point since most of the automated sitemap creation services crawl whatever junk is on your site or those files that shouldn't be indexed such as robots.txt, htaccess, etc. Do it manually and you won't regret submitting a sitemap.
Agree with Mystique..... But for dynamic sites its not possible to create an XML file manually. I suggest create a script which crawl's all your pages from db and then this scripts writes each URL individually in XML format. Better if you people go through Google guidelines on http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=156184.
i think it reconsider all links that are already indexed and it re index thts why this problem i think