Been getting this error. There are only about 10 posts I haven't read.
An Error Has Occurred!
The server's resources are temporarily under too high a demand to find all the topics you have not read.
Try using "Unread posts since last visit" rather than "All unread posts"? I'm sure the former makes less demand on the server.
As mentioned in yesterday's similar posts, "since last visit" gives me typically 2-3 pages whereas "all unread" finds 1700 pages!
I always use posts since last visit.
I always use 'Show all unread posts' and there's very rarely more than 2-3 pages when it's busy.
Have to say it's brassing me off at present as, by the time I've waited for pages to load, got error messages, timed out notices etc I'm spending 3 times as long as I need to on this verdammt laptop.
I've always used show all unread posts as for some reason the show posts since last visit seems to miss loads out. I don't usually have an issue.
I always use '... since last visit', as 'Show all unread posts' is a lot slower.