Here's the scenario:

I have a form with two drop-down menus.

Drop-down menu #1 holds all main categories.

Drop-down menu #2 holds all sub categories

I want drop-down menu #2 to only show categories that belong to the selected item in drop-down menu #1.

Demo:  http://jsfiddle.net/Hm3rA/1/

When I get rid of the old selected item, the drop-down menu breaks.
E.g When I added:

1. //Remove the old selected attribute
2. $(oldSubCategorySelected).removeAttr('selected');

If you remove that line, the drop-down almost does what I want, however it's still got the old sub-category selected.

Would anyone know of how to remedy this? Perhaps I'm going about it the wrong way?