Not sure what happens. In my Google Webmaster Tools I have over 50 Crawl Errors.
Any changes in xml-sitemap plugin. Google found links like a (error of course):
where 'literatura' is category and 'czym-jest-qask-pl' is custom page (not plugin, just standard page created in admin).
I have other Q&A sites, and no problem like this. Any idea what happens?