I have just realized that the encodeURIComponent doesn't encode properly for the URL...
I think that it's very important to have a function that encode for url, a mix between escape and encodeURIComponent.
I know that the problem doesn't came directly from jquery, but it's a bug, for the ISO-8859-1 encoding (used in europe) it's a big problem, the param function (and all function that use it) becomes useless!
Like i said the form plugin use it in the ajaxSubmit function and so i can't use it without takingg care, in my target page, of the decoding.
Thanks and sorry for my english :S