This is probably a simple one, but I can't find any rhyme or reason for it.
I have several combo boxes on a form. After creating a record the user may want to come back and clear out the data in it.
One of the attrobutes looks like this when it is selected:

It has a little 'x' that you can click on to clear it.
The other combo boxes though look like this:

There is no 'x' to clear them.
What is it that triggers that 'x' to be there or not be there?
One thing I do notice is that when I move the mouse over the Case Assistant attribute it gets 'greyed' out, like it has been selected. But on the Attorney Assigned attribute just the 'x' appears, so it could be clicked on to clear it.
There must be some setting that causes this difference in bahavior.