We are going to release a new micro-revision of mailman 2.1 series by the end of this year (month ... December). I wish you the translators can spare a little time to update your language mailman.po files. The mailman.pot template file was already generated in the mid-November and merged into the each language po files. You can download it with the latest code from CVS (Release_2_1-maint branch). Or, if you are uneasy downloading from CVS, I've made a tar ball for this version at: http://mm.tkikuchi.net/mailman-2.1.6a.tgz
You can update mailman.po directly on CVS if you have the privilege, upload it in the SF patch tracker area, or send me (firstname.lastname@example.org) by email at your convenience.