On 16 April, Colin Watson wrote that, in accordance with the technical board decision documented in https://lists.ubuntu.com/archives/ubuntu-devel-announce/2008-March/000400.html, individuals using the PowerPC (also known as PPC) build of Xubuntu should take care to update their /etc/apt/sources.list file. Old sources.list entries looked like this:

/etc/apt/sources.list. Old sources.list entries looked like this:

deb http://archive.ubuntu.com/ubuntu/ gutsy main restricted

... while new entries should look like this:

deb http://ports.ubuntu.com/ubuntu-ports/ hardy main restricted

If you are still using archive.ubuntu.com on a PowerPC system, beware that the old sources list is likely to stop working soon and you should migrate to ports.ubuntu.com as above.

You can open your sources.list by pressing Alt+F2, entering gksudo "mousepad /etc/apt/sources.list" and pressing Run. You can then replace the mentioned lines with their new values.