Just solved an issue on a machine upgraded via yum from FC4 to FC5 tha had been bugging me for ages. The symptoms were that gnome power manager would fail with a message saying that dbus was not running and that eval `dbus-launch –auto-syntax` needed to be run.
The other symptom I noticed was that dbus-monitor or anything else that connected to dbus session would fail with a ‘connection refused’ message.
After trawling round the net, I found a Redhat Bugzilla posting that resolved the issue – between FC4 and FC5 the location of dbus-daemon had moved from /usr/bin to /bin (and also dbus-cleanup-sockets). The yum upgrade for the dbus packages had not removed the FC4 versions from /usr/bin so a quick rm /usr/bin/dbus-daemon and rm /usr/bin/dbus-cleanup-sockets followed by a reboot sorted the problem altogether.
Perhaps that should be added to the Yum upgrade FAQ on Fedora wiki. Another small but annoying problem resolved 
