I know this is an old thread, but I've found the same problem. It is very annoying, but I would like to add an even more annoying sorting issue: If I choose "Last Post Time", "Descending", "Beginning", it will just go back to whatever it was before. This is the way every other forum I've ever visited sorts their messages by default, so I find it very odd that I can't select it here. The closest I can get is "Thread Start Time", "Descending", "Beginning".