Since Ubuntu 11.10 multiarch support becomes set by default in new systems as well as in upgraded ones. This sounds like a nice feature, but it breaks one of my favorite tools: aptitude. As of now, aptitude can't handle multiple arches of the same package and therefore runs wild when told to do any task.

The solution to this is to disable multiarch for the time being. This is done by the following command:

mv /etc/dpkg/dpkg.cfg.d/multiarch /etc/dpkg/dpkg.cfg.d/multiarch.backup && apt-get update

In case aptitude learns how to handle multiarch some day, it can be re-enabled by running the command the other way round.