Jquery ui多选小部件在IE中慢速滚动

I am using jquery ui multiselect widget on a page which has been constructed with jquery ui layout plugin. a portion(or rather a sub-pane) of the page which contains this widget is scrollable. so when i click on the multiselect it opens the dropdown. now when i start scrolling with dropdown still open, the dropdown stays in it's position and thus gets detached from the dropdown button. To fix this i added a function on scroll event of that div. it fixes this issue but kills the scroll performance in IE, the code is as followsI am using jquery ui multiselect widget on a pa