Sorry but if my theory is correct there is nothing I can do about this.
But, Taz, I thought you could do everything. :)
Must admit, it does play up though, Taz. On mine, it'll show me all new posts, but as soon as I make a post myself, they all disappear leaving me to find the unread ones. This doesn't always happen. Sometimes, midway through a session, four or five new posts pop up as other people post, and these tend not to disappear at all, even once I've read them.
As I'm in here at roughly the same times everyday, though, it doesn't really bother me. I just go by the dates that are showing on the threads.
Something that does annoy me at times is the clock that gives the times of my posts. For ages it has been an hour out, even though I had clicked on the correct zone in My Account. I figured it would sort itself out once we changed the clocks last weekend, but now I'm 2 hours out. I don't want to mess around with the settings in My Account because it'll mess up my avatar (besides I did try altering the time zone settings once before and nothing seemed to happen)
The clock in my PC is working fine, by the way.