Yes please do tell!  This is all very strange...

Thanks.  I got it to work with this:

upstream ajentiweb {
    server 127.0.0.1:8000 weight=1 fail_timeout=300s;
}
server {
    listen 80;
    server_name    domain.com;
    add_header Strict-Transport-Security max-age=2592000;
    rewrite ^/.*$ https://domain.com/ permanent;
}
server {
    listen        443;
    server_name   domain.com;
    client_max_body_size 200m;
    access_log    /var/log/nginx/ajenti-access.log;
    error_log    /var/log/nginx/ajenti-error.log;
    ssl on;
    ssl_certificate        /etc/nginx/certs/domain.com/server.crt;
    ssl_certificate_key    /etc/nginx/certs/domain.com/server.key;
    keepalive_timeout    60;
    ssl_ciphers            HIGH:!ADH:!MD5;
    ssl_protocols            SSLv3 TLSv1;
    ssl_prefer_server_ciphers    on;
    proxy_buffers 16 64k;
    proxy_buffer_size 128k;
    location / {
        proxy_pass    http://ajentiweb;
        proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forward-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto https;
        proxy_redirect off;
        proxy_read_timeout 5m;
    }
}