As I discussed in a recent post BP…

As I discussed in a recent post, BP 1.5′s slug setup is a bit different. To ensure full compatibility with all BP 1.5 setups (and specifically, those with hierarchical page structures – such as, you’ll need to change the way you concatenate links.

The most straightfoward way to do this is by using BP 1.5′s new bp_get_x_root_slug() functions, eg
$group_admin_link = bp_get_root_domain() . bp_get_groups_root_slug() . '/' . $this_group_slug . '/admin';

However, using bp_get_groups_root_slug() means that your plugin will not work with earlier versions of BP, which will show a fatal ‘undefined function’ error. If you need to continue to support earlier versions of BP, you might want to think about assembling your links like this:

global $bp;
$group_slug = function_exists( 'bp_get_groups_root_slug' ) ? bp_get_groups_root_slug() : $bp->groups->slug;
$group_admin_link = bp_get_root_domain() . $group_slug . '/' . $this_group_slug . '/admin';

Similarly, the recommended way to check for the current component in BP 1.5 is to use the component-specific functions:

if ( bp_is_groups_component() ) { ...

or, for arbitrary components,

if ( bp_is_current_component( $component_slug_or_root_slug ) ) { ...

However, if you need to retain backward compatibility for the moment, try something like the following:

if ( ( function_exists( 'bp_is_groups_component' ) && bp_is_groups_component() ) || $bp->current_component == $bp->groups->slug ) { ...

I’ll probably be doing this myself with some of my more popular plugins, as a stopgap release until I feel more comfortable dropping backward compatibility with pre-1.5 installations of BuddyPress.