Mike,
The issue at present is with forum posts that contain images. The more images per post and the more posts per page, the slower those pages load. To ameliorate the problem until I can find a permanent solution I have reduced the number of posts per page to 2. This makes the pages load faster, benefits those who just want to reply to the last post or two but means there is more navigation if you wish to go back a handful of posts.
I will keep it like that for now and switch it back to normal as soon as I can.
Kind regards
David