[Conkeror] Error when running custom command

[foss[ilized]]

I followed the tip at:

http://conkeror.org/Tips#ManipulateProxySettings

for configuring the proxy settings interactively. But when I enter
values for the proxy server and the proxy port, via the following
command sequence:

(1) M-x set-proxy-session

(2) server: localhost

(3) port: 8118 [for privoxy]

I get the following error:

NS_ERROR_UNEXPECTED: Component returned failure code: 0x8000ffff
(NS_ERROR_UNEXPECTED) [nsIPrefBranch.setCharPref]
set_branch_pref()@chrome://conkeror/content/utils.js:491
default_pref()@chrome://conkeror/content/utils.js:501
session_pref()@chrome://conkeror/content/utils.js:558
set_proxy_session()@chrome://conkeror/content/rc.js ->
file:///home/cachalot/.conkerorrc:20
anonymous()@chrome://conkeror/content/rc.js ->
file:///home/cachalot/.conkerorrc:38
_do_call()@chrome://conkeror/content/coroutine.js:278
anonymous()@chrome://conkeror/content/coroutine.js:410
exit_minibuffer()@chrome://conkeror/content/minibuffer-read.js:436
anonymous()@chrome://conkeror/content/minibuffer-read.js:439
call_interactively()@chrome://conkeror/content/interactive.js:133
keypress_handler()@chrome://conkeror/content/keyboard.js:518

I'm running the Debian conkeror package 0.9~git090223-1 with the
xulrunner package 1.9.0.6-1. Is this a known problem? Thanks in
advance.