Hi
You can try to start up tvheadend like this:
[root@mythpc ~]# tvheadend -f -u hts -g video -C
The -C option gives you world-wide administrative access.
-C              If no useraccount exist then create one with
                 no username and no password. Use with care as
                 it will allow world-wide administrative access
                 to your Tvheadend installation until you edit
                 the access-control from within the Tvheadend UI
The rest of the option can you chech with 
[root@mythpc ~]# tvheadend -help
 -C              If no useraccount exist then create one with
                 no username and no password. Use with care as
                 it will allow world-wide administrative access
                 to your Tvheadend installation until you edit
                 the access-control from within the Tvheadend UI
Best regards 
Harald