Thank you very much for your help!
@ Brian:
So "A: Breaks: B" is meant to read as "A would break B if it was going to be
installed". I interpreted the "Breaks:" as "does not comply with the need
for the following dependency".
Well, I'm not a native speaker. So maybe I should not complain about error
messages that seem confusing to me. Thanks again for the explanation.
@ Ron:
I tried to install the package "shutter" from testing on my stable distro. I
included the testing repositories in the apt-sources list and set
APT::Default-Release "lenny";
Then:
---snip---
cassowary:~# apt-get --simulate install shutter
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
libc6-i386: Breaks: lib32asound2 (<= 1.0.20-2) but 1.0.16-2 is to be
installed
Breaks: lib32gcc1 (<= 1:4.4.0-6) but 1:4.3.2-1.1 is to be
installed
Breaks: lib32gfortran3 (<= 4.4.0-6) but 4.3.2-1.1 is to be
installed
Breaks: lib32gomp1 (<= 4.4.0-6) but 4.3.2-1.1 is to be
installed
Breaks: lib32stdc++6 (<= 4.4.0-6) but 4.3.2-1.1 is to be
installed
E: Broken packages
---snap---