I found a solution to this problem, You don't need to uninstall or install any thing at all.
First you go to your profile edit on windows live you chose your preferred language and change it, save it to your profile Then Close your Messenger down.
second and last action you open your
control panel-->add/remove software or program you find windows live messenger select it and hit repair open your messenger again wupti the language on your windows messenger is changed
i hope i could help with my bad English.
