First of all, really great work - using an author taxonomy is a very nice design. And the real-time search is definitely an improvement over the dropdown.
The bad news: it only works on some installations -- not others. I've tested this plugin on several installs with the most current version of WordPress (3.2.1) all default JS files and all other plugins turned off with the same exact theme running. All the other function calls work well with the plugin.
The only variance I can see is the LAMP Stack. Here's what works and what doesn't:
1) Commercial Host: WORKS
2) MAMP localhost: DOESN'T WORK
3) Windows NT: DOESN'T WORK
Wondering if the plugin needs MySQL 5.0.92 for it to run OR an older version of PHP?
Would really like to understand the variance and happy to help troubleshoot.