Comment 22 for bug 407418

Ok, I fixed the problem. It turned out that I had in fact python-qt4-common installed (which seems to only exist in jaunty), and it wasn't that I needed it, but that it somehow interfered with the karmic packages. So, after doing:

sudo apt-get remove python-qt4-common

everything worked again:

Python 2.6.2+ (release26-maint, Sep 9 2009, 22:58:56)
[GCC 4.4.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from PyQt4 import QtCore
>>> dir(QtCore)
['PYQT_VERSION', 'PYQT_VERSION_STR', 'QAbstractEventDispatcher', 'QAbstractFileEngine', '
...]
>>>

(btw. my first example was actually wrong it seems, but software-notifier-kde and software-properties-kde did exit with the error message mentioned in this bug report. )