Navigation problem after upgrading to wordpress 3.1.X

Hi everyone, I am facing terrible problems with navigation after i have upgraded my wordpress to 3.1.x. Some how it seems that the next_posts_link() and previous_posts_link() dont seem to work, i have set the setting so as to display 5 posts at a single page in my category, with the next entry and previous entry option , but these links get redirected to a 404 page not found…

I would be more than happy if someone could provide me with some quick help..
Heres the link to the page .. http://theludhiana.com/ne/category/blog/
when i click the page 2 option it gets redirected to 404..