There's an earlier thread on this ("New Posts not working?"), but more importantly, the reason is discussed in the "Why Was FlyerTalk Down?" thread on this forum.

Apparently, at some point the system needs to be taken down for a couple of hours to perform the necessary database repairs, but the appropriate (least disruptive) time hasn't been decided on yet.... or something along those lines.

Guess we just need to be patient. (Besides, the "New Posts" feature, while nice, isn't THAT critical.)