If it's like other forums I've been a
mod/admin on, it's mostly do to a refresh cycle. Some forums have a set number of times a day that it will refresh and update user capability and changes.
Other than that you might want to check the stickies on the top of this forum to see the "how many posts do i need"
thread and it might be able to shed some light if it is a post based issue (or something similar)