Hi, with some help from Alex Greif offlist helping me reproducing the issue, I decided to reinstall the system using a different mirror and different approaches.
After lot of trying I found that I am running into the issue as soon as I install either quodlibet or keepassx on my system. Removing those packages and restarting X fixes the error messages. So, the combination of jwm, messagebus (with the dbus-session configured in my xinitrc) and either quodlibet or keepassx shows the problem for me. I have reproduced this now at least 3 times. I don't know what to make of this but I would put this issue into the packages area. So it probably makes more sense to move this to ports@. Since I am oviously not a developer I have no idea how to properly debug this. My trial and error method doesn't get me anywhere closer to the real issue. Maybe the issue will disappear with later package builds and updates. Sorry I cannot be of better help. Lars
