Request #20059:  Peculiar window hiding in Windows GUI (Win32)

Create a Listener, Select Usage->GeneralPreferences->Compiler (or any
option under Usage->GeneralPreferences or Usage->ToolPreferences), and 
a MLWorks Preferences window appears.  Position this window on top of 
the Listener and select the same option again.  The Preferences window
should be brought to the front if it wasn't already.  Also when first 
selected the Preferences window should not be obscured by the Listener.
