If I try and force certain areas of my site to use https I get
Error 310 (net::ERR_TOO_MANY_REDIRECTS): There were too many redirects.
If I just us
Try adding
fastcgi_param HTTPS on;
To your nginx vhost, that will help Symfony recognize that the request is a SSL request, symfony is checking against the HTTPS global variable to check if the request is SSL or not and redirect acordingly, if that variable is not set inside by the webserver on a SSL request symfony will try to redirect causing the loop :)
More info over here.. http://blog.servergrove.com/2011/04/04/symfony2-quick-tip-generateurl-with-https-on-nginx/