WordPress Problems a javascript error?

Hi,

My blog (WP 2.8.6) has some problems:

The WYSIWYG editor isn’t loaded properly, you can find a screenshot of what i get:

http://img23.imageshack.us/img23/6060/sanstitre1li.jpg

Also, when I try to install a new plugin, the description page isn’t loaded in th eusual overlay but go behind at the end of the page (screenshot below)

http://img189.imageshack.us/img189/2053/sanstitre2ff.jpg

I’ve disabled all installed plugin but the problem is the same,, I reinstalled WP and the problem is stil the same, Have you any idea of what can I do?

cheers
Anita