KDE CVS from 2004/01/17, using KMDI from kdelibs. IDEAl mode. Open some files. Switch to one of them (but not to the last), select "Close All Others". All files will be closed except the last one. It's even visible that first there is a switch to the last one and closing starts after that. Haven't tested with non-IDEAl mode.
I cannot reproduce this - using a KDevelop from recent cvs and kdelibs cvs from last week. How do you choose "close all others" - from application menu or from context menu within the file? What editor did you use?
I'm pretty sure this is fixed.