1. Load the attached testcase 2. Focus and select the entire listbox. 3. Scroll down towards the bottom, but not all the way (if you see "SCROLL UP" um...scroll up). 4. Deselect an option like HTML Editing or HTML DOM, the listbox will jump all the way to the top, though the option is deselected properly. 5. If you scroll all the way to the bottom, it only jumps to the top if you deselect the SCROLL UP option.
Created attachment 12797 [details] Reduction
<rdar://problem/4971222>
Committed revision 19520.