Sometimes when I pick a topic to go to, and if it has atleast 10 pages or so it takes me to a page with a list of all of the pages instead of taking me to the last page. Another thing about it is that there are two lists. I don't think it's my computer since this has happened on more than one computer.
It's been known to happen. There are two sets because the top set is at the top of the page and the bottom set is from the bottom of the page. However, with AG3 coming around the corner, fixing this isn't a priority.
It happens when moderators or admins delete comments from a thread. There's a bug in the code that recalculates how many pages exist for a given thread, so when you click on 'last post' it thinks the forum message really had 10 pages when really there are only 9, etc.
To echo Gantic, this isn't a priority. We'll address it in AG3.