Transparency not working with Xfce 4.8

Forwarded from Debian's BTS: http://bugs.debian.org/661271

According to the bug reporter, transparency doesn't work when using Xfce. (Note that I'm unable to confirm whether or not this is the case as I'm a GNOME user.) conkyrc provided by the bug reporter is as follows:

$ cat ~/.conkyrc
background yes

alignment top_right
gap_x 75
gap_y 70

use_xft yes
xftfont Sans:size=8
xftalpha 1
text_buffer_size 2048

update_interval 3.0
total_run_times 0

double_buffer yes

own_window yes
own_window_transparent yes
own_window_type normal
own_window_hints undecorate,sticky,skip_taskbar,skip_pager,below

minimum_size 5 5
maximum_width 180

draw_shades yes
draw_outline no
draw_borders no

border_width 0
border_inner_margin 0
border_margin 0
stippled_borders 0

default_color white
default_shade_color black
default_outline_color white

no_buffers yes
uppercase no
cpu_avg_samples 2
net_avg_samples 2
use_spacer yes
override_utf8_locale no

TEXT
${font sans-serif:bold:size=8}SYSTEM ${hr 2}
${font sans-serif:normal:size=8}Kernel: ${alignr}${kernel}
Host:$alignr$nodename
CPU: ${cpu cpu}% ${alignr}${cpubar 8,60 cpu}
RAM: $memperc% ${alignr}${membar 8,60}
Uptime: ${alignr}${uptime}

$ conky -V
Conky 1.8.1 compiled Sat Dec 3 12:13:33 UTC 2011 for Linux 3.1.0-1-amd64 (x86_64)

Compiled in features:

System config file: /etc/conky/conky.conf
Package library path: /usr/lib/conky

X11:
* Xdamage extension
* XDBE (double buffer extension)
* Xft
* ARGB visual

Music detection:
* Audacious
* MPD
* MOC
* XMMS2

General:
* math
* hddtemp
* portmon
* Curl
* RSS
* Weather (METAR)
* Weather (XOAP)
* wireless
* config-output
* Imlib2
* apcupsd
* iostats
* ncurses
* Lua

Lua bindings:
* Cairo
* Imlib2