This is not the behaviour described in earlier bugs #21703 and #22660. KPortage starts and filters ebuilds according to package status (installed/masked etc.) correctly. After that, whatever you try to emerge only gets displayed in the output tab window as "these are the packages I would merge" followed by the list, i.e. only the --pretend behaviour. It stalls after that, interrupting the process with the stop button in the toolbar doesn't work. No difference whether it's started as root or via kdesu. KPortage 0.6.1, Python 2.2.3, Portage 2.0.49-r3, Kernel 2.6.0-test4-mm5
KPortage is a external project. As you can read on their website: http://www.nongnu.org/kportage/ the people behind KPortage have not enough time anymore, to work on it. Go on and help them. :)
Yeah, unfortunately kportage is not actively maintained at the moment. It could use a maintainer...
Unfortunately this is a but in kportage and not within gentoo itself. Someone will need to take over maintainership of that project in order to fix this problem.