I click on the last post button to skim past all the old pages in a long thread and get to the last post (since there is no last post viewed option.) Pretty handy.
But on and off, when I click on the amount of minutes from the last post, I get a solid white page with "Error 404" in the top left. It happens mostly in the PS Lounge but occasionally here and in the Acrobat/Reader forums.
Not a huge deal but something you may want to look in to at some point.
Hint: but giving us a last viewed option would be even better of course.