Ajax control toolkit auto complete dropdown vertically misaligned

Question

Ajax control toolkit auto complete dropdown displaying in random vertical positions.

Below is the css which I use currently

    .completionList
    {
        background-color: #fff;
        border: solid 1px #444444;
        margin: 0px;
        padding: 2px;
        height: 100px;
        overflow: auto;
    }
    .listItem
    {
        color: #666666;
    }
    .itemHighlighted
    {
        background-color: #ffc0c0;
    }