I’m not sure if you found a solution for this yet. But I had a similar issue and found a solution. On my site, I only allow wholesale customers to view certain categories. I was able to accomplish this by adding this extension.
All you have to is specify which customer group can view the category or products.
Also, if you want to only allow access to users that you approve, there is another extension from the same author which allows you to activate a newly registered user before they can browse your storefront.
Please note, you need to set your magento connect manager to “beta” in order for the install to go through.
So far, I am very happy with these extensions.