Something weird has started happening with my multilevel lists.

When I'm using a multi-level list at the moment and finish a paragraph, if I hit enter it should go to the next line and give me a new number. Instead, it goes to the next line and does not give me a new number and the font changes. It works OK if I start a new word in the old paragraph and put the cursor before the word and then press enter. But otherwise not.

Also, at some times when I do it it appears to insert a page break!?

Any ideas?