Итак, подопытные:

/usr/local/nginx/sbin/nginx -V
nginx: nginx version: nginx/1.1.6
nginx: built by gcc 4.2.1 20070719 [FreeBSD]
nginx: TLS SNI support enabled
nginx: configure arguments: --with-http_ssl_module --with-cc-opt=-Wno-error --add-module=/usr/local/lib/ruby/gems/1.8/gems/passenger-3.0.8/ext/nginx --with-http_flv_module

uname -a
FreeBSD endyhost 7.0-RELEASE FreeBSD 7.0-RELEASE #3: Sun Aug 10 23:51:17 MSD 2008 root@endyhost:/usr/obj/usr/src/sys/ENDYKERN i386

/usr/local/apache-peruser/bin/apachectl -V
Server version: Apache/2.2.19 (Unix)
Server built: Aug 24 2011 20:50:01
Server's Module Magic Number: 20051115:28
Server loaded: APR 1.4.5, APR-Util 1.3.12
Compiled using: APR 1.4.5, APR-Util 1.3.12
Architecture: 32-bit
Server MPM: Peruser
threaded: no
forked: yes (variable process count)
Server compiled with....
-D APACHE_MPM_DIR="server/mpm/experimental/peruser"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_FLOCK_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=128
-D HTTPD_ROOT="/usr/local/apache-peruser/"
-D SUEXEC_BIN="/usr/local/apache-peruser//bin/suexec"
-D DEFAULT_PIDLOG="logs/httpd.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_LOCKFILE="logs/accept.lock"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="conf/mime.types"
-D SERVER_CONFIG_FILE="conf/httpd.conf"

/usr/local/php/bin/php -v
PHP 5.2.13 (cli) (built: Jul 6 2011 01:23:35)

tcpdump при успешной передаче/парсинге параметров:
http://trinex.ru/nginx-apache-tcpdump.success.log

и при провале:
http://trinex.ru/nginx-apache-tcpdump.fail.log

Лог nginx в debug mode (он, правда, относится только к проваленному тесту):
http://trinex.ru/nginx.error.log

PS:
Andrey Repin> http://ru2.php.net/manual/en/ini.core.php#ini.always-populate-raw-post-data

$HTTP_RAW_POST_DATA is not available with enctype="multipart/form-data".

Если нужна дополнительная информация - готов её предоставить.