This was discovered on the community site here. Recently a member sent a spam message to me and you deleted the user I suppose. Now it shows a notification that I have a message, and when I click on the message to view it says it no longer exists, because you deleted the spam user. However, that's where it is stuck, I have no way to delete that notification from showing and my messages is always saying I have one unviewed.
Solution? - Thanks... Gary
Purge the database!
Also an option to purge the database of old content by options in admin. So you could keep good topics, etc but not news post. Freeing space!
Thanks for you report, we will fix this issue on next version.
Thanks,
Kent,