Wow, you mean the plugin actually deleted the items out of your activity tables? To the best of my knowledge there is nothing in this plugin that’s even capable of deleting a single activity item.
I’ve been looking around, and in fact, all of the activity is still in the tables, it just seems to be an issue with displaying them. And it appears I was hasty in blaming this plugin, because when it’s deactivated, the problem still exists. It was just time-coincidental, may have been a cache issue.
The issue is in fact to do with the filter dropdown. You have to change it to get anything to show. Which again is solved by clearing the cache. Will have to look into that separately.
Sorry if I sounded accusatory!
Another thing is that under admin, where you can send a message to all users regardless of their settings, the tab says ‘email options’, which doesn’t really fit to the function of that tab.
Alex
Phew, that’s a relief 
Good suggestion about the Email Options tab.