This was getting really annoying, so i simple reinstalled my system yesterday. I directly installed Ubuntu 15.04. The problem is gone now. So it must be a configuration. Either something i did which cannot remember (i can not see a reason is should have fiddled with that), or something introducing during the 15.05 development process. I still suspect the timeframe around the systemd switch. It might be helpful to know that 1) the problem did not exist with 14.04 or 14.10 (upgraded from 14.04) but 15.04 since systemd switch (upgraded from 14.04, then 14.10).
@kaiserclaudius: sadly did not try to used upstart on this machine, but we have a second machine with a similar issue, i will try this there as soon as i find the time.
This was getting really annoying, so i simple reinstalled my system yesterday. I directly installed Ubuntu 15.04. The problem is gone now. So it must be a configuration. Either something i did which cannot remember (i can not see a reason is should have fiddled with that), or something introducing during the 15.05 development process. I still suspect the timeframe around the systemd switch. It might be helpful to know that 1) the problem did not exist with 14.04 or 14.10 (upgraded from 14.04) but 15.04 since systemd switch (upgraded from 14.04, then 14.10).
@kaiserclaudius: sadly did not try to used upstart on this machine, but we have a second machine with a similar issue, i will try this there as soon as i find the time.
@carlix: Does Lubuntu use systemd?