Dynamic Menu Admin is a module designed for sites with outstandingly large 
amount of menu entries. Stock Drupal 6 does not particularly like having more
than about 200 entries but even if that were fixed, rendering more than 200
is very likely to crash IE6 and some 7 users due to slower JS engines. 

After enabling the module you will find new links on the Menu Admin page which 
will allow you to expand/collapse branches of the menu system so that at any
point your browser will not have to render too much information.