Oops, sorry about that; I thought you meant to simply add "debug" to the log directive in the .conf.

But! I updated to 0.8.31 and rebuilt with --with-debug (as per your recommendation) and everything works perfectly.

Here's my final nginx.conf if anyone else will want to do something similar in the future.

location /eve/ {
proxy_pass http://127.0.0.1:9001;
proxy_intercept_errors on;
error_page 504 = @fallback;
}

location @fallback {
rewrite ^(.*)$ /backend.php;
}

Kind of a messy rewrite, but for my purposes, it's fine. Thanks for all the help, and happy 2010 =)