While trying to do a “do-release-upgrade”, to upgrade to Ubuntu Precise, I encountered a error that Google did not find a satisfactory answer for:

An unresolvable problem occurred while calculating the upgrade:
E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the command 'ubuntu-bug update-manager' in a terminal.

The problem was I had some packages installed that had no upgrade path, that is, are not available in Precise. To debug this I looked in the /var/log/dist-upgrade/apt.log file, and it identifies the packages that were “broken”. I just had to “apt-get remove” them, do the release upgrade, and afterwards I could reinstall them.

Problem solved.