Matt Hmm, well the unread post count is an add-on, and it's nothing to do with the core product. I'll report it to the author of the add-on.
Matt Chris D said: Old bug, unfortunately. I have it sort of fixed in a newer version but it caused another bug but I've been too busy to sort it. The 1 unread post they are seeing is an unread post in a soft deleted thread. Workaround is to simply mark all forums read.
Dave_Gilbert im at 262 new posts so i wont see that problem for a wile, i did get it down to about 15 a few months back hahaha.