Scrollbar doesn`t show up when data is updated

[Ozge]

Combobox has only one item at the beginning. When it is updated dynamically, it has about 50 items and the scrollbar doesn`t show up.

var combobox = $("#input").data("kendoComboBox");
combobox.dataSource.data(ObjList); //now about 50 items
combobox.dataSource.query();
combobox.height = 200;
combobox.refresh();

Browser mode: IE8 compatibility
Document mode: IE8 standarts

Any suggestions to fix it?
Thank you.