dbus isn't working

[Marko Käning]

Suddenly KDE4 apps wouldn't run anymore.

I diagnosed that the user-started dbus-daemon isn't running in my system anymore, although launchd should start it as usual.

Running it manually reveals: 
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markos-imac:~ marko$ /opt/local/bin/dbus-daemon --nofork --session
Failed to start message bus: launch_msg("CheckIn") IPC failure: Operation not permitted
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and I am wondering WHY this is happening now.