File.Copy(lstCopyFiles.SelectedItem.ToString(), lstDestination.SelectedItem.ToString(),true);

On that line, is lstDestination.SelectedItem.ToString() giving you a full path or just the directory to put it in. It may be that you are only telling it the target directory, when you need to specify the whole thing..

I.e, for parameter 1: "C:\BILL\JOE.TXT"

for parameter 2: "C:\JOE\JOE.TXT" is ok but "C:\JOE\" is not ok..

Bill