HTML editor breaks my xHTML, why?

Hi,

I have a new blog over at http://fruitsfrais.org/blogue with the French version of WP 2.5.1 and I edit my articles with the HTML editor (with the html editing actually).

However, it seem to do some weird things that breaks my xhtml. For example, here is a post in the editor:

[…]C’est une façon simple et véritable de promouvoir votre fureteur favori!
<p style=”text-align: center;”><img title=”Journée de téléchargement” src=”http://www.spreadfirefox.com/files/images/affiliates_banners/180x150_02b_fr.png&#8221; alt=”Journée de téléchargement” /></p>

But once I publish it, the image tag ends up like that:

<img title=”Journée de téléchargement” src=”http://www.spreadfirefox.com/files/images/affiliates_banners/180x150_02b_fr.png&#8221; alt=”Journée de téléchargement”/ >

This is not proper closing of the tag and the slash has been moved for unknown reasons.

Any help would be greatly appreciated.