Trouble with wp-admin/nav-menus.php

I have a huge amount of text in my blog (about 10 Mb in 30 publications), and when I go to ‘wp-admin/nav-menus.php’ to make a custom menu, I’ve got only part of the page, and the following error:

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 1619953 bytes) in /usr/home/mylogin/mysite.com/www/wp-includes/formatting.php on line 417

A short investigation shows, that the scripts are loading a content of many (maybe all) posts for unknown reason 🙂