title: SelectedItem is not visually highlighted when set programmatically
body: <p>I am using silverlight 4 listbox control to display list of terms, On selection of one term, I am calling an ria service to 
  fetch similar words for that term and loading those similar terms for the other listbox. for one requirement I need to auto 
  fetch the similar terms for the default or the first term in the terms listbox. I am achieving the same by selecting the 
  first item of the itemsource although I have one issue where when I am programmatically setting the listbox selecteditem, 
  its getting set, however visually the selected item is not getting highlighted. Any Ideas why the selected item is not 
  getting highlighted when set programmatically. </p>
  
  <p>The items change when I hover over them for the terms listbox.</p>
  
  <p>note: I have attached one poc app demonstrating the above issue, when I run the poc app the similar terms for the first
  term in the terms listbox are displayed. however the first item in this case "red" is not visually highlighted, when I click
  the terms listbox for the UI the first item shows surronded by a transparent rectangle.</p>
  
  <p>Things I have tried thing</p>
  
  <p>I have used the VSM for specifying the SelectedUnfocused state for the ListboxItem Style and applied that style to the
  itemcontainerstyle property of the listboxItem.</p>