automatic update want to remove packages

[Joep L. Blom]

I have a problem with update.
I wanted to install libreoffice from the repositories but synaptic 
wanted to remove my openoffice installation before it installed 
libreoffice and I wanted to have both in parallel.
  So I installed it directly from the site and that went without any 
problem.
Update showed then 2 problems.The first - not related to libreoffice - 
is that it could only do a partial update because there were problems, 
not specified, causing some updates not to be installed.
The second, however, is worse because it would remove all openoffice 
packages and some more for no apparent reason.
Is Ubuntu now determining which packages I have on my system?
Libreoffice runs apparently without a problem and openoffice also (I 
haven't yet tried both together as that is maybe asking for trouble).
Anybody know how to prevent this behaviour of update and synaptic?
Joep