Vanilla 2

I had some probs with IE and managed to solve in this way:

original:
left_pos = cur_x + settings.offset_left + scrollPos['scrollLeft'];
top_pos = cur_y + settings.offset_top + scrollPos['scrollTop'];
$('.prettyLoader').css({
'top':top_pos,
'left':left_pos
});

changed in:
left_pos = cur_x + settings.offset_left + scrollPos['scrollLeft'];
top_pos = cur_y + settings.offset_top + scrollPos['scrollTop'];
if (!isNaN(left_pos)) $('.prettyLoader').css({'left': left_pos});
else $('.prettyLoader').css({ 'left': '' });
if (!isNaN(top_pos)) $('.prettyLoader').css({ 'top': top_pos });
else $('.prettyLoader').css({ 'top': '' });

sometime a NaNpx value was set and this is illegal. Just in case this is useful to someone else too.