The new volume plugin prevents starting of fbpabel when /dev/mixer is not available. This is the case on all distributions that use PulseAudio, in my case Fedora.
Creating profile 'default' at /home/chris/.config/fbpanel/default
Using /usr/share/fbpanel/default as template
volume: can't open /dev/mixer
fbpanel: can't start plugin volume
The volume plugin should not be enabled by default or it must not prevent fbpanel from starting.