auto page numbers don't work for one chapter in book

I've got one document in the middle of a book in which the pages don't autonumber correctly, event though the all the other chapters in the book do. In other words, it runs like this:

Ch. 1:  pp. 1 - 4

Ch. 2:  pp. 5 - 10

Ch. 3:  pp. 1 - 6

Ch. 4:  pp. 17- 22

In Ch. 3, when I go into the Page tab of the Numbering Properties dialog box, the First Page # radio button is checked, and the first page number is "1". I delete the "1", click the Continue Numbering from Previous Page in Book radio button, and click Set. Nothing changes in the document, and when I reopen the Numbering Properties box, the First Page # button is still checked, and it's still set to "1". Saving the file doesn't make any difference, nor does closing it and reopening it.

Any ideas about what the problem is?