There is no 404 error for nonexisten blog. Try to chek it here: http://demo.boonex.com/blogs/entry/hereisnoentry and you you'll get 200.
Same here: http://demo.boonex.com/blogs/posts/TTTTTTT and here: http://demo.boonex.com/blogs/member_posts/222
And why dolphin generates 2 different URLS for 1 page?: