Moshu, I'm glad you know the code but that's not very helpful to me :-)
Moreover if WYSIWYG had problems with HTML tags creation, it wouldn't be helpful at all. (I always use HTML editor, however).
Could you please tell me how to safely turn the WYSIWYG off?
The workaround that I found is to write a dummy post without links, list and image, so that a new well-configured DB entry is create, and then enter the real HTML post directly into the database.
The next thing I would (ehm) "like" to do is to have a look at the php files and see what's happening... but I still hope that somebody else, more skilled than me, already did this and could help me.
I forgot to say that this behaviour takes place with or without plugins and not only affects links, lists and images but also text formatting (italic, bold, ...).
Thank you.