The English translation of Messenger Plus! is saved in the DefaultLg file that is in the Resources folder. This file will always work with the version of Messenger Plus! it came with.
Other language files, and this includes this Hax0r Language file, contain a small text string like
code:
CompatibilityLevel=3087
that specifies for what version they are made. If the version of Plus! you are using is newer or older then the CompatibilityLevel doesn't match and you will not be able to change the language to the one with the faulty compatibility level. This means that it won't show up in the list of available languages. This is the problem here.
You should change that string in the language file yourself to make it work with the new version of Plus!. Simply go to Notepad and change that value (it's almost in the beginning of the file). For Messenger Plus! 3.40.112 BETA the compatibility level is 3106. However, although you'll be able to use the language then, note that some translations may be missing or incorrect because the language file was not made to be used with the one you are using
/ 
