Thanks for the quick response. I am not using a caching plugin. I just realized that the activity stream of private groups is shown in the built-in activity stream too, so it has nothing to do with your plugin. I will report it on the general bp forums.

Thank you for a great plugin!
However, I think I found a bug.

When users are logged out, the activity stream is still displayed, even if “Limit to Logged In user’s activity” is checked.
Even activity for private groups is displayed!

I run WP 3.2.1 and BP 1.5.1