As long as it doesn’t happen again it’s not serious, but I’m curious what might have happened. Recently I was sorting a list of 123 items into a preferred order, then used Bullet and Numbering to make a list. It only came to 122, I didn’t know why but I didn’t want to cross-reference to see what was missing, so I listed it as it was, with the fact there was 1 item missing. Someone else pointed out later that there were indeed 123 items, but my list had gone …100, 101, 101, 102… If I’d numbered them myself I’d have just assumed that was carelessness on my part, but how would Word make such a mistake?
Word can start a new list at any number desired, and playing with the order may have caused it to restart the list at 101 inappropriately. Try right-clicking on the second 101 and using the “continue previous list” menu selection – play around with that for a while and see if it helps.
If matt_mcl’s fix doesn’t work, you may have a List Template problem.
In some versions of Word, when you’ve managed to build up a large number of List Templates (the underlying code that supports your bulleted and numbered lists), you can see some very strange list behaviors - lists not accepting renumbering, bullets of incorrect style, bullets where they don’t belong, or refusal of the application to apply bullets where they do belong, and so on.
You can grow a large-ish collection of List Templates simply by refreshing lists many times (F9 is not always your friend), or re-ordering them, and so on. Also, copy and paste from another Word document can carry along some List Templates (always Copy>Paste Special>Unformatted Text. It’ll save you grief!).
You can find out how many templates you have via a Visual Basic for Applications (VBA) query, but that’s not really helpful unless you’re a specialist. If you suspect you’ve got this problem, you can simply do the following:
Save the document as HTML.
Close the document.
Close all instances of Word.
Reopen the document from the HTML.
Save the document as Word (*.Doc).
Reapply any formatting lost.
That will strip out the superfluous List Templates.
THIS IS NOT A GUARANTEED FIX!
Word is weird, to say the least. This is a low-effort fix you can try, that will cause you minimum grief, and won’t wipe out your work. You might very well have other problems, too.