yes thank you! i guess i just forgot to put the root directive...
or better for my case to set the alias:
location ~ ^/phpmyadmin/(.*)(\.php)$ {
alias /usr/share/phpmyadmin/;
fastcgi_pass upstream_backend;
etc...
}
Posted at Nginx Forum: http://forum.nginx.org/read.php?2,188514,188695#msg-188695