After implementing perusio's config for d7+boost, module installation fails

When I login with admin role and navigate to Modules > Install Module, pick a local file and then click Install I get redirected to /authorize.php?batch=1&op=start&id=12 which generates a 404. This happens with perusio's drupal.conf as well as drupal_boost.conf. Reverting to MKTecknology's very basic nginx.conf restores functionality.

System details:

Running Arch Linux:

$ uname -a
Linux charon 3.2.13-1-ARCH #1 SMP PREEMPT Sat Mar 24 09:10:39 CET 2012 x86_64 Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz GenuineIntel GNU/Linux

$ nginx -V
nginx version: nginx/1.1.18
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --pid-path=/var/run/nginx.pid --lock-path=/var/lock/nginx.lock --http-client-body-temp-path=/var/spool/nginx/client_body_temp --http-proxy-temp-path=/var/spool/nginx/proxy_temp --http-fastcgi-temp-path=/var/spool/nginx/fastcgi_temp --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --user=http --group=http --with-imap --with-imap_ssl_module --with-http_ssl_module --with-http_stub_status_module --with-http_dav_module --with-http_gzip_static_module --with-ipv6 --http-scgi-temp-path=/var/spool/nginx --http-uwsgi-temp-path=/var/spool/nginx --with-http_mp4_module --with-http_realip_module --with-http_addition_module --with-http_xslt_module --with-http_image_filter_module --with-http_geoip_module --with-http_sub_module --with-http_flv_module --with-http_secure_link_module --add-module=/var/abs/community/nginx/nginx-upload-progress-module --add-module=/var/abs/community/nginx/nginx-upstream-fair --with-http_degradation_module --with-file-aio

$ php -v
PHP 5.3.10 with Suhosin-Patch (cli) (built: Feb 6 2012 19:18:12)
Copyright (c) 1997-2012 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2012 Zend Technologies

$ php-fpm -v
PHP 5.3.10 (fpm-fcgi) (built: Feb 6 2012 19:19:30)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2012 Zend Technologies

$ drush --version
drush version 5.1

Drupal version is 7.12