It may be so that the translation functions for these strings are missing in your releases. You should update to WPMU 2.8.1 (or 2.8.2) and BP 1.0.3 anyways.
WPMU translation files should reside in:
and BP translation files should reside in:
If you’d like more help, please provide a link to the language files you are using, and where and what strings are not translated.