I updated my pretty links structure. The posts which has some cross references have been updated, however some of the search engine crawlers are reporting 404 errors on my earlier older pretty link structure trackback address.
http://www.mysite.com/blog/post-name/trackback (Old url reporting 404 error now)
http://www.mysite.com/blog/category-name/post-name/trackback (working fine)
Thanks in advance.