[jquery] drag'n'drop + slider -> $.widget is not a function

[mlipreri]

Ciao,
non risco a capire perchè includendo questi js

    <script src="jquery.js" type="text/javascript" charset="utf-8"></script>
    <script src="jquery.dimensions.js" type="text/javascript" charset="utf-8"></script>
    <script src="ui.mouse.js" type="text/javascript" charset="utf-8"></script>
    <script src="ui.slider.js" type="text/javascript" charset="utf-8"></script>
    <script src="ui.core.js"></script>
    <script src="ui.draggable.js"></script>
    <script src="ui.droppable.js"></script>

ottengo questo errore

$.widget is not a function
[Break on this error] _refreshValue: function(animate) {
ui.slider.js (riga 499)
$.widget is not a function
[Break on this error] _uiHash: function(event) {
ui.draggable.js (riga 391)
$.widget is not a function
[Break on this error] ui: function(c) {

Questo anche cancellando tutto il mio codice js dalla pagina....
Ho notato che se cancello

    <script src="ui.mouse.js" type="text/javascript" charset="utf-8"></script>
    <script src="ui.slider.js" type="text/javascript" charset="utf-8"></script>

non ottengo nessun errore, ma mi serve uno slider nella pagina...
Qualche dritta?
thx