There are some little flaws in the language files. Some of them are from threads 6.x

admin/changeusergroups.php
// CCFIXME is this file used?
admin/availablelangs.php
// RB is this file necessary?
admin/gen_display.php
line 3 contains br without selfclose
newpost.php
empty string $ubbt_lang['MARK_POSTS'] = "";
newreply.php
empty string $ubbt_lang['MARK_POSTS'] = "";