shaz, doing
set(handles.yourListbox, 'Value', []);
used to work in older versions, and I did use it. Why? For example if you loaded a listbox with files, selected a high number (say 20), and then changed folder and reloaded the listbox and it had fewer files, the listbox would vanish if there were fewer files than the number you selected. For example the new listbox had only 19 items and your "Value" property was still at 20. So what I did was to deselect all by setting the value property to []. However they made some change a few versions ago and this no longer worked. I had to set the value equal to 1. But that still selected an item and sometimes you don't want an item selected. For example it might imply that some things displayed on your GUI apply to that selected item, when they don't.
However the good news is that setting the value to [] now works again, as of R2012b. I just tested it to verify, and it works again! Please upgrade to that version.
