BuddyPress.org

To re-iterate but in the forum as good form dictates:

It looks as though you are missing the rules that style these elements and which are contained in default.css they start from the line:

/* > Data Tables

There is a good chance, as they appear to specify in percentage widths and are not descendant selector dependent, that they should drop in to whatever stylesheets you have, but you may need to play around a bit with them.