Retrievig subitem from ListView works, but only once!

Question

in my lvConcepts_SelectedIndexChanged(..)
I have ...
   MessageBox.Show(lvConcepts.SelectedItems[0].SubItems[0].Text);
 
It works the first time I click on the ListView.  If I click again I get
"An unhandled exception of type 'System.ArgumentOutOfRangeException'
...   InvalidArgument=Value of '0' is not valid for 'index'."
 
What is going on!?
Thanks for any help.