I use jquery selectmenu plugin. I have initialized select with
$('select').selectmenu({width:100, maxHeight:300, style: 'dropdown'});
I have many options and this causes to appear default browser scrollbar, but i cant use it. If I click and try to drag this bar, selectmenu closes. I can scroll with mouse wheel. There might be some conflict in css and various plugins. But im not sure where to start looking.
Any ideas, what might be causing this problem?
You can set the max-height for the content of the selectmenu when it is opened in CSS and then it will present a scrollbar within the list of items that can be used.
ul.ui-menu { max-height: 420px !important; }
You might need to further restrict this style-change in your CSS if you are using other jQuery UI widgets that include a <ul> element with the class 'ui-menu' assigned.