Thank you. Your instructions have fixed the problem.
First I executed
/sudo apt-get clean/
Then I ran the software updater. It failed again:
The package system is broken
If you are using third party repositories then disable them, since
they are a common source of problems.
Now
Public bug reported:
This all started when I used Software Updater earlier this week. (I use once
weekly to keep system up to date).
Looks as if update of GNOME multi protocol chat and call client (nautilus-send
to plugin) nautilus-sendto-empathy initiated the problem. (I am not even aware
that
