Due to some files being corrupted on the host server, I was forced to reinstall the software for the board. The majority of the data (Threads, posts, users, etc) is stored remotely on the database but avatars are the one thing stored locally and were consequently lost, and you will need to reup them to display them.
It is for the same reason that many of the smilies are gone...we will have them fixed as soon as possible.