Thanks Holle, but I also saw this problem if I made a new post in a hidden area. And also, theory as well as experiment show this...
As I say, look in the UPI2DB files I mentioned - the way it works is that the function set_unread() adds to the UPI2DB database every recent post (i.e. whenever the function is called) - assigning a user_id (of the reader) to the post, so that it can be flagged as new or unread to the reader, depending on age and last logon. There is absolutely nothing to check for the view authorisation, so any new post made will get added to the UPI2DB unread table, and will appear as a new/unread post to the user, regardless of whether it is to a normal area or hidden area. So I can't see how it can be XS specific, nor down to using the lite version - even the full version has no view authorisation checking. If theres no authorisation checking, then theres no authorisation checking, and I can't see how else it can differentiate whether a user should be assigned to a post they cannot read in the unread_posts table. Does this make sense, or is this a case of me being completely mad in a world of sanity, (which to a philosopher is just as valid in the opposite sense)
Because fundamentally it doesn't check permissions, the problem will of course flag posts that have been moved to hidden areas as well! Maybe there is a difference because of the newer versions of UPI2DB. I'm using XS059rc3, but I see that 059 upi2DB files are identical to 058 anyhow, so the problem should be seen if you are using 058, and you create a completely hidden forum - with view auth of the forum and everthing within being admin. Make some new posts. Then log in immediately with a regular user test accout (depending on the likelihood of another user posting, confusing the issue!). You should see a few new posts counted at the top, and when you click to see them, you are told you cannot view them. Funnily enough, I cannot see the problem on this site, beause I'll have to go through all the 394 unread posts counted for me!
I've been a bit busy with other things at the moment, but I have a fix in mind (for me then, as it seems to be just me that sees this), and will try it hopefully soon!
Thanks for your help