Lines 55-56 of ui.slider.js say:

//Make nodes selectable by expression
$.extend($.expr[':'], { slider: "(' '+a.className+' ').indexOf(' ui-slider ')" });

indexOf() returns -1 on failure, which evaluates to true, and the result is that $(':slider') selects every element on the page. Adding >=0 fixes the problem:

//Make nodes selectable by expression
$.extend($.expr[':'], { slider: "(' '+a.className+' ').indexOf(' ui-slider ')>=0" });