Some icons appear as default win icon

On a couple of our NT 4 SP6 machines, ones without the Active Desktop installed, some desktop icons appear as the default windows icon. Some of these are files, others are shortcuts to programs. For instance, there are 4 .oft files (outlook message templates), and sometimes 1, 2 or all three will appear as the default windows icon. The standard icons like My Computer or Neighborhood Network appear OK. When I hit F5 some are fixed – I have to hit F5 3 or 4 times to get all the icons back. Itried deleting the ShellIconCache file, even by stopping explorer.exe using Task Manager, then opening a command prompt and deleting it, then restarting. I can find nothing helpful in the Microsoft KB.