You can do one of two things:
1/ remove the float from #header and replace with ‘overflow: hidden’
Or
2/ add ‘clear:both; to div.activity in the bp styles, creating the ruleset if it doesn’t exist.
You can then do what you did in applying ‘list-style: none;’.
This is pretty much a consequence of mixing style from essentially two different themes, you may well run into other issue as well.
What puzzles me is that the theme you have used here states in it’s header ‘tags’ line ‘BP’ if that is the case and it is BP compatible then you have no need to run the BP template pack.
