/usr/bin/GEM/_logout.app is thought for initiating a GEM logout. You better 
use _logout.app (e.g. as a logout popup item in SMU's Start.set or insert 
it in ~/.bash_logout) instead of logout.app or otherwise logout.app will be 
executed twice: first if you start it by yourself, secondly by gemsh.app 
during its exit procedure. _logout.app just sends an AP_TERM message to 
GEMSH.
