emergency–page editing problem

Hopefully this problem is mine, as I am having a problem with a site that is being used for a fund raiser tomorrow.

I created a page and when I tried to make it a child of another page I found only 20 items listed in the menu (the site has roughly 40 pages). Looking at other pages previously created, I found some menus worked (listed all pages) while others did not.

Any ideas?

Bill