I was having the same problem after upgrading from Debian Squeeze to Wheezy on a headless armel SBC that I've been using as a sound server. Purging the configs doesn't do anything.
It seems a per-session D-Bus daemon must be running for the user trying to start pulseaudio. This is normally started automatically when you start X, but that doesn't happen if you're going headless.
Here's the answer:
http://ubuntuforums.org/showthread.php?t=1743072
I had to install the dbus-x11 package, but I'd imagine you'd already have that if you have a headful setup.
I wrote a quick script to handle starting a D-Bus daemon and exporting the required variables, and call it to start a pulseaudio daemon. It could probably use some better fault handling and clean up, but it works fine for my use case. You will need to manually cleanup though, otherwise you'll have a new D-Bus daemon started every time you run this script.
Code:
#!/bin/bash
dbusinfo=( $(dbus-launch) )
DBUS_SESSION_BUS_ADDRESS=${dbusinfo[0]#DBUS_SESSION_BUS_ADDRESS=}
DBUS_SESSION_BUS_PID=${dbusinfo[1]#DBUS_SESSION_BUS_PID=}
export DBUS_SESSION_BUS_ADDRESS
export DBUS_SESSION_BUS_PID
pulseaudio --start
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