It seems like YouTube has changed how they display subscribers in the new layout. Instead of displaying page by page, they display all subscribers up to the page you request. Therefore, their servers are having an issue displaying subscribers after a certain number of pages because there is too much information to display.
We have posted the issue on Google’s help forum - http://groups.google.com/a/googleproductforums.com/forum/#!category-topic/youtube/feedback--suggestions/9o8SjQ0QLR4
Unfortunately there is nothing that we can do until YouTube fixes the bug in their system.