BuddyPress.org

If you upgrade your theme to the version that is in RC2 you can take advantage of the new member template functions that are available to you. The directories now have their own little templates located in /buddypress-member/directories/<directorytype>/<directorytype>-loop.php file.

Then all the template tags you find in /bp-core/bp-core-templatetags.php are available to you. That particular function you were using doesn’t exist anymore. The underlying call still works which is:

BP_XProfile_ProfileData::get_value_byfieldname( $field, $user_id );

so

BP_XProfile_ProfileData::get_value_byfieldname( ‘One Line Summary’, $user->user_id );

Should work. I encourage you to look at the new directory code and templates.