OOUI's DropdownWidget has some height issues on Internet Explorer 10. Here is one example from Content Translation header, when menu handle is clicked (It retains bigger height until focus is lost):
Here are more height problems from demo page on IE10, where height problems are visible even on hover, not only on click. The only widget I click on gif below shows same behavior as personal menu handle on Content Translation.
Note: In the gif above, I click only on widget marked with label "DropdownWidget (disabled options)". All the rest are only hovered.