Emacs starts with current screen contents in its display buffer

[Segundo Bob]

My system:

        GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.10.7)
 of 2014-03-07 on toyol, modified by Debian

        Xubuntu32 14.04

I installed Xubuntu32 14.04 on 2014-06-12.  I noticed this problem 
almost immediately.  The screen contents belonging to other applications 
is NOT in the emacs buffer that is saved to disk, but it is displayed. 
This makes emacs unusable for me.

I have spent several hours over these past weeks Googling for anyone 
reporting a similar problem, but I have found no relevant information. 
This probably means that my problem is not a widespread problem with the 
Ubuntu release.

Who is supposed to clear the "display buffers"?  Linux or Emacs?

I will appreciate any help.
--
Segundo Bob
SegundoBob@gmail.com