I’ve got the same problem. I don’t see either a “Write Post” page (I’m trying to edit a new post that simply won’t honor the paragraph breaks I insert in the draft, after many attempts. I don’t see any “paragraph format” option anywhere, either. Help!
On the Advanced toolbar, on the left-hand side. If you only have one row of buttons in the visual editor, click the one on the far right, with the multicoloured buttons.
If you are copy/pasting from a word processor, that’s your problem right there. You’re introducing HTML errors into the blog. To fix them and prevent more from being added, go to Settings->Writing and select “WordPress should correct invalidly nested XHTML” and save. Then Edit that post, changing anything at all, and Update. That forces the change to take effect.