Here's the situation:
Some time ago I apparently posted something in someone's blog (or photo album) and checked the little box that would alert me if anyone else posted in the entry.  Meanwhile, the owner of the blog apparently made the blog entry (or photo album, if that's the case) private - for "friends only."  Now I'm getting alerts that someone posted in the entry, but I can't view the posting - which means I can't get rid of the alert that shows up under "New Comments."  Nor can I un-tick the check box, meaning all future comments give the same problem.

That is an odd one. Of course there is the option to just request to be "friends" with the poster, but in your case... seems there should be some way on your end to stop tracking something.

I think this is a bug that's never happened before, but yeah getting temporarily added to their friends list should work. You also could ask the user to make the content public just long enough for you to unsubscribe.

Thanks, y'all.  But I'm not looking for a workaround.  I think the bug should be fixed.

yes, we should fix it. :) please submit a bug report with the details of the blog/album involved so we can work on a fix. thanks and sorry!