I have found a problem that would stop us going live with our application. Basically when the Editor is hidden and then shown again the behaviour of the Bold and underline buttons are changed.

 

This can also be replicated on:

http://richtextbox.com/test/use-display-none.aspx

To reproduce:

1. Enter text "The quick brown fox jumps over the lazy dog"
2. Highlight some text and click the 'Bold' button
3. The HTML will be as follows: "The q<strong>uic</strong>k brown fox jumps over the lazy dog"
4. Hide the Editor and then show it again.
5. Highlight some text and click the 'Bold' button
6. The HTML will now be as follows: "The q<strong>uic</strong>k brown f<span style="font-weight: bold;">ox </span>jumps over the lazy dog"