Not showing focus

I have a weird situation here. I have section of code that initially is
described by the class "aaa". That class is:

..aaa {
background-color:#DDDDDD;
position:fixed;
top:200px;
visibility:hidden;
z-index:99;
}

The entire block is initially hidden and then made visible by clicking
on a button to do te operations desired. It show in the middle of the page.

Now for the problem. In this block there is a textarea input and a text
input. In both cases when you move the mouse over it, the indicator
changes from an arrow to an I-beam. This is what you would expect.
However, when I click into either one focus is not indicated (the solid
vertical line). I can type into these boxes and the input is accepted.

What could cause that vertical bar that indicates focus to not be shown?

This is part of a large proprietary application so I can't give a URL.
There are no other classes inside the block. I am asking if anyone has
come across something like this before and how they fixed it.

I have cross-posted to the javascript newsgroup in case there is a
javascript solution.