Can't Select 1st List Value in Dropdown When Tabbing into it

This seems to be a consistent problem. I want users to be able to either click on or tab into a dropdown field. If they tab in, they should be able to type in values rather than hitting the arrow on the dropdown box. But it seems they can't choose (aka type in) the first item in the list. I don't provide a default value. The drop down is blank initially. But, for instance, if I have a drop down which is a series of numbers 1,2,3,4,5,6,7,8,9,10,11...20,21.... and so on they can't type 1. They just get a tone and nothing is typed in. They CAN type 2 THEN 1 (which cycles through all values starting with 1 which is what should happen when they type in 1 in the first place). Why is that and how can I correct it?