Versions dropdown disappears when clicking on scrollbar in IE

When project has huge number of version and drop-down has scroll-bar while creating issue, clicking on scroll-bar using the mouse in IE will disappear the drop-down version list.

To reproduce:
1) Go to the Create Issue page in IE8 and IE9
2) Click the Affect or Fix Versions
3) Click the scroll-bar to show the drop-down menu
4) Attempt to scroll the drop-down by dragging the scroll-bar, or clicking in an open space on the scroll-bar gutter, the drop-down will disappear