Issue: Activity Feed in areas & sub areas empty

I can only duplicate this if the user has permission to view the sub-area but doesn't have permission to view the wiki home page (which I don't think would let you view the sub-area enough to see the feed in the first place). In any case, this would cause a database error due to an empty where clause.

This is fixed in the next release. As for other triggers (perhaps corrupt data), they are unnatural and unfortunately can't be caught at this time without more information. Perhaps if you could post the AJAX response from the XHR tab on Firebug, I could see why it's happening for you.