HA Proxy does not start up on Ubuntu 13

I am trying to launch HA Proxy 1.4.24 on an ubuntu 13 VM via sudo. My haproxy.cfg file is copied below. However, when I use sudo service haproxy start or try sudo /etc/init.d/haproxy start, the process not start up. Any ideas on troubleshooting this would be helpful. The config file appears to pass the configuration test (sudo haproxy -f haproxy.cfg -c results in "Configuration file is valid").
Also, Enabled flag in the haproxy file in /etc/init.d is set to 1.
Port 80 does not appear to be bound by any other service.

Update: I had set the enabled flag to 1 in the /etc/init.d/haproxy file as opposed to in the /etc/default/haproxy file – fixing this change allowed me to run haproxy normally.

global
    maxconn     25000 # Total Max Connections. This is dependent on ulimit
    daemon
    nbproc      4 # Number of processing cores. Dual Dual-core Opteron is 4 cores for example.

defaults
    mode        http
    clitimeout  60000
    srvtimeout  30000
    contimeout  4000
    timeout http-request 5s  # added to tackle slow http requests
        option abortonclose
        option forwardfor


listen  http_proxy *:80
        #bind *:80
    balance roundrobin # Load Balancing algorithm
    option httpchk
    option forwardfor # This sets X-Forwarded-For
        default_backend bk_web

# Dynamic part of the application
backend bk_web
    ## Define your servers to balance
    balance roundrobin ## change to URL hashing
    cookie MYSRV insert indirect nocache  ## check this NOTE TO SELF
    server server1 0.0.0.0:81 weight 1 maxconn 512 check
    server server2 0.0.0.0:82 weight 1 maxconn 512 check