Scrolling using keyboard does not work in autocomplete JQgrid

Scrolling using keyboard does not work in autocomplete JQgrid

I am not able to scroll the Autocomplete list of items using keyboard down/up arrow. In my JQgrid i have a textbox with autocomlete functionality. When the auto suggestion list appears, I am able to scroll through the list of items using mouse. But the scrolling doesn't happen when I use Keyboard. Please Help. My CSS portion for auto complete is
 
  1. .ui-autocomplete

    {
        position
    : absolute;
        max
    -height: 200px !important;
        overflow
    -y:auto !important;
        overflow
    -x: hidden;
        padding
    -right: 5px;

    }