I ran into a similar problem. It works on one server and does not on another server with same Nginx configuration. Found the the solution which is answered by Igor here http://forum.nginx.org/read.php?2,1612,1627#msg-1627
Yes. Or you may combine SSL/non-SSL servers in one server:
server {
listen 80;
listen 443 default ssl;
# ssl on - remember to comment this out
}