Fixed the avatar thing. It was working when I tested it after setting up the forum, but subsequent things I did stuffed it up.
gb, there was an issue like that quite a while back that went away after a forum reinstall. However, this one seems different--searching with other usernames works fine. It seems to have to do with the length of your username--visit the memberlist and try it on other two-character usernames. Did it work in the past? I noticed one of the updates in the most recent release of phpBB had to do with making searches less server-intensive, and perhaps ignoring very short strings was part of it.
EDIT: Yep. I tried some two-character usernames in the memberlist in phpBB's own forum, and no results when searching for posts. So it's not my fault