dhtmlxCombo, dhx_combo_list, IE height problem

Suite and Optimus Suite 5
#1

When I set min-height( .dhx_combo_list) to less than 147px, In IE (6,7) there is vislible another unknown element under div.dhx_combo_list.

#2

There is a hidden iframe under list ( it resolves issue with native selectboxes in IE )
This element can be accessed as
    combo.DOMlistF
It has the same css class applied   -    ‘dhx_combo_list’