This is the screen-saver activating, and is 
normal behavior as far as I can discern.

often, the thin client we use at the Lab 
Attendant's station will blacken its screen, then 
show an icon with a monitor and what looks like a 
stack of drives.  Once in a while there is a  
little green check mark that appears.  Most often 
it quickly returns to the previous icons, and 
after a while (1-30 minutes) the MASH session 
will re-appear on the screen as if nothing had 
changed.  kelmore@wou.edu, computerlabs@wou.edu 
for contact info.  "Student, Student" refers to 
myself, Kevin E.