Comment 6 for bug 102573

I think this problem is being caused by the multi-notifier plugin, as removing it has cured the problem.

pete@pete-laptop:~$ apt-cache showpkg sylpheed-claws-gtk2-multi-notifier
Package: sylpheed-claws-gtk2-multi-notifier
Versions:
2.6.0-1 (/var/lib/apt/lists/gb.archive.ubuntu.com_ubuntu_dists_feisty_universe_binary-i386_Packages) (/var/lib/dpkg/status)
 Description Language:
                 File: /var/lib/apt/lists/gb.archive.ubuntu.com_ubuntu_dists_feisty_universe_binary-i386_Packages
                  MD5: f09aaed9346a3785bb1e01dc68952b27

Reverse Depends:
  sylpheed-claws-gtk2-multi-notifier-dbgsym,sylpheed-claws-gtk2-multi-notifier 2.6.0-1
  sylpheed-claws-gtk2-extra-plugins,sylpheed-claws-gtk2-multi-notifier 2.6.0-1
Dependencies:
2.6.0-1 - libc6 (2 2.5-0ubuntu1) sylpheed-claws-gtk2 (2 2.6.0)
Provides:
2.6.0-1 -
Reverse Provides: