Yes, we have a certain membergroup that we want to offer products to only, and it's unfortunately set as a secondary membergroup.
The secondary group is our "Official Members" and we have to place it secondary so that it works with our ranking system and the stars shown for each group.
When I last tried to set it up, I gave only "Official Members" access to the category but when I tested with a test account it only worked if "Official Members" was the primary membergroup. Unfortunately, the way I have things set up, I cannot move "Official Members" to be a primary group or it won't work with our system setup.
Our membergroup system is pretty complex because we use it for not only forum membergrouping, but for the actual organization itself.