Those of you who were still having problems with avatars not showing up, please download the ZIP file again. It includes new code for the phpinclude_start template that parses properly on servers running versions of PHP older than 4.3.2
Apparently 4.3.1 and older versions of PHP didn't like the syntax I used when calling the image.php file to grab a user's custom avatar. I have replaced that code with some that works a little better across all versions.
Confirmed to work on my own test server.