xchat does not remember "enable logging" and "display scrollback" settings

In the Preferences dialog, under Channels -> Logging, when I turn off the checkboxes "Display scrollback from previous session" and "Enable logging of conversations to disk", they have no effect and are checked again when I restart XChat. Also the conversations are logged, and previous scrollback is displayed.

However, when I set irc_logging = 0 in my ~/.xchat/xchat.conf, logging is off, and also the checkbox is unchecked. But I was not able to identify the setting which affects the "display scrollback" option.

$ lsb_release -rd
Description: Ubuntu 10.04.3 LTS
Release: 10.04

$ apt-cache policy xchat
xchat:
  Installed: 2.8.6-4ubuntu5
  Candidate: 2.8.6-4ubuntu6~ppa2
  Version table:
     2.8.6-4ubuntu6~ppa2 0
        990 http://ppa.launchpad.net/rohieb/ppa/ubuntu/ lucid/main amd64 Packages
 *** 2.8.6-4ubuntu5 0
        990 http://de.archive.ubuntu.com/ubuntu/ lucid/universe amd64 Packages
        100 /var/lib/dpkg/status

xchat-common:
  Installed: 2.8.6-4ubuntu5
  Candidate: 2.8.6-4ubuntu6~ppa2
  Version table:
     2.8.6-4ubuntu6~ppa2 0
        990 http://ppa.launchpad.net/rohieb/ppa/ubuntu/ lucid/main amd64 Packages
 *** 2.8.6-4ubuntu5 0
        990 http://de.archive.ubuntu.com/ubuntu/ lucid/universe amd64 Packages
        100 /var/lib/dpkg/status