"edit.php" is gone after installing nrelate

Hi,

My problem is that after installing nrelate, my “edit.php” is gone.
But it still work at “edit.php?post_type=page”.
I would like to know what happened with it?
How can i repair this problem?

Thanks a lot!

http://ww.wp.xz.cn/extend/plugins/nrelate-related-content/