can't install new languages (nothing happen)

Confirmed.
Output from the terminal :

** Message: pygobject_register_sinkfunc is deprecated (GtkWindow)
** Message: pygobject_register_sinkfunc is deprecated (GtkInvisible)
** Message: pygobject_register_sinkfunc is deprecated (GtkObject)
/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py:777: GtkWarning: gtk_cell_view_set_cell_data: assertion `cell_view->priv->displayed_row != NULL' failed
  cell = combo.get_child().get_cell_renderers()[0]
[]
[<Package: name:'nabi' id:4904>, <Package: name:'libhangul0-data' id:6532>, <Package: name:'libibus1' id:2856>, <Package: name:'ibus-gtk' id:2858>, <Package: name:'ttf-alee' id:4858>, <Package: name:'language-pack-ko-base' id:4259>, <Package: name:'language-pack-gnome-ko-base' id:4258>, <Package: name:'language-support-input-ko' id:4903>, <Package: name:'im-switch' id:2678>, <Package: name:'python-appindicator' id:2860>, <Package: name:'ibus' id:2855>, <Package: name:'ibus-hangul' id:2863>, <Package: name:'language-support-fonts-ko' id:4856>, <Package: name:'language-pack-ko' id:4261>, <Package: name:'python-ibus' id:2857>, <Package: name:'ttf-unfonts-extra' id:4857>, <Package: name:'x-ttcidfont-conf' id:1259>, <Package: name:'libhangul0' id:2868>, <Package: name:'language-pack-gnome-ko' id:4257>]

$ gnome-language-selector
/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py:777: GtkWarning: gtk_cell_view_set_cell_data: assertion `cell_view->priv->displayed_row != NULL' failed
  cell = combo.get_child().get_cell_renderers()[0]
[]
[<Package: name:'openoffice.org-l10n-fr' id:9161>, <Package: name:'language-support-writing-fr' id:4969>, <Package: name:'language-pack-gnome-fr' id:4176>, <Package: name:'openoffice.org-thesaurus-fr' id:9102>, <Package: name:'language-pack-fr-base' id:4175>, <Package: name:'hunspell-fr' id:2846>, <Package: name:'openoffice.org-hyphenation-fr' id:9090>, <Package: name:'gnome-user-guide-fr' id:2531>, <Package: name:'language-pack-gnome-fr-base' id:4177>, <Package: name:'openoffice.org-l10n-common' id:9231>, <Package: name:'openoffice.org-help-fr' id:9065>, <Package: name:'wfrench' id:1415>, <Package: name:'language-pack-fr' id:4174>]
^CTraceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/aptdaemon/defer.py", line 535, in _inline_callbacks
    result = gen.send(result)
  File "/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py", line 624, in commit_aptdaemon
    self._run_transaction(trans)
  File "/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py", line 602, in _run_transaction
    time.sleep(0.02)
KeyboardInterrupt

The interesting thing is, when I press Ctrl+c, it throws some errors but does start actually installing right packages.

$ gnome-language-selector
/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py:777: GtkWarning: gtk_cell_view_set_cell_data: assertion `cell_view->priv->displayed_row != NULL' failed
  cell = combo.get_child().get_cell_renderers()[0]
Here I press Ctrl+c
^CTraceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/aptdaemon/defer.py", line 535, in _inline_callbacks
    result = gen.send(result)
  File "/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py", line 624, in commit_aptdaemon
    self._run_transaction(trans)
  File "/usr/lib/python2.6/dist-packages/LanguageSelector/gtk/GtkLanguageSelector.py", line 602, in _run_transaction
    time.sleep(0.02)
KeyboardInterrupt

Why is such a horrible bug marked with low-importance? I'm up-to-date (2. September, 2010) and can't change the language from English to German. I don't really care if I work on a English- or a German-laptop, but I'm sure there are thousands of users who care!

Thanks
Tom

I'm getting the same behavior here with latest image. confirming the bug

This bug was fixed in the package language-selector - 0.6.3

---------------
language-selector (0.6.3) maverick; urgency=low

  [ Martin Pitt ]
  * data/LanguageSelector.ui, LanguageSelector/gtk/GtkLanguageSelector.py: Add
    a Close button. (LP: #345113)

  [ Michael Vogt ]
  * fix aptdaemon install/update (LP: #612825)
 -- Michael Vogt <email address hidden> Fri, 03 Sep 2010 18:54:47 +0200

i still cannot change the language on maverik 10.10!
i installed spanish language and removed uninstalled english, restarted pc and english is still the languange! what the hell?
i read here the bug has been solved but not on my pc..

@Dorian: This was a bug in he development version, have you installed from a release version or a development version, and is your system fully updated.
Check that you language is selected when you login.
The binery files are in US english so you can not remove that. When you uninstall the English files you uninstall othere dialects of English.

Try opening up the /language-selector/ and make sure that your language is on top of the list.