Hello,
I'm formatting my wifes dissertation (it has to be in on Monday) and am
having problems with numbering sections.

A simplified form of the current structure is:

I Part One
1 Heading
1.1 Heading
1.1.1 Heading

II Part Two
2 Heading
2.1 Heading
2.1.1 Heading
3 Heading
3.1 Heading
3.1.1 Heading

III Part Three
4 Heading
4.1 Heading
4.1.1 Heading
5 Heading
5.1 Heading
5.1.1 Heading

I want it to look like this:

I Part One
1 Heading
1.1 Heading
1.1.1 Heading

II Part Two
1 Heading
1.1 Heading
1.1.1 Heading
2 Heading
2.1 Heading
2.1.1 Heading

III Part Three
1 Heading
1.1 Heading
1.1.1 Heading
2 Heading
2.1 Heading
2.1.1 Heading

When I try and re-number the sections The number becomes 1 briefly and then
becomes whatever it was before.

****
Why?
****
This is driving me round the bend!

I trie again and managed to get it to look like this:

I Part One
1 Heading
1.1 Heading
1.1.1 Heading

II Part Two
1 Heading
1.1 Heading
1.1.1 Heading
2 Heading
2.1 Heading
2.1.1 Heading

III Part Three
3 Heading
3.1 Heading
3.1.1 Heading
4 Heading
4.1 Heading
4.1.1 Heading

Here section I and II are now how I want but if I try and change section III
I get this:

I Part One
1 Heading
1.1 Heading
1.1.1 Heading

II Part Two
2 Heading
2.1 Heading
2.1.1 Heading
3 Heading
3.1 Heading
3.1.1 Heading

III Part Three
1 Heading
1.1 Heading
1.1.1 Heading
2 Heading
2.1 Heading
2.1.1 Heading

Anyone know why or how I can fix it. Any help appreciated ASAP. Would
copying the text into a new file and re-making the heading styles and
applying them help?