I had an urgent need to fix this issue quickly so I added a few lines of code to one of the Drupal Commons files directly. Once I have more time I plan to extract the functionality into a custom module. Until then this was my fix:
Open file /profiles/drupal_commons/modules/features/common_core/commons_core.blocks.inc
Locate functions '_commons_core_group_activity_block_view()' and '_commons_core_group_members_block_view()'.
Add the following lines before the if statements:
//Determine group nid
$url_parameter = explode("/", $_GET['q']);
$group_nid = $url_parameter[1];
//Determine group membership, exclude Admins
$is_group_member = og_is_group_member($group_nid,$include_admins = FALSE);
Add && ($is_group_member != '')
as second condition to each if statement
If you know a better way please share.
Alex