Theme text formatting disappears

Since this seems to be a common problem, at least for me, I’ll ask the question and hope for a more or less universal answer that fixes the problem whenever I run into it.

Just spent close to half an hour changing themes and reformating the page text, using Copywriter. (WP 2.8.4) Pasted it into the new theme, previewed it, and all the formatting disappeared. The text was bunched together, no line spacing, no formatting at all. (Theme is Pet Charms 2.0 from FreeWP Themes)

This is not the first time I’ve run into this problem. Other Themes I’ve tried also ignore text edits, especially Page text edits. Is there something I should be doing prior to editing the text. Ideally, I’d like a WYSIWYG, but I don’t guess that’s going to happen anytime soon, or it would’ve happened by now.

It’s a very frustrating, time consuming problem. If you have a fix, I’d sure appreciate knowing about it. Thanks

Wes