Lai panāktu korektu darbu:

No root konta:
1) cd /usr/local/lib/python2.7/dist-packages/deluge-1.3.14-py2.7.egg/deluge/ui/web/

2) cp json_api.py json_api.py.BACKUP

3) aizkomentējam (atceļam) sekojošas 3 rindas:

if request.getHeader('content-type') != 'application/json':
        message = 'Invalid JSON request content-type: %s' % request.getHeader('content-type')
        raise JSONException(message)

Risinājums atrasts te:
http://forum.deluge-torrent.org/viewtopic.php?t=54428