Have forced http to https?
Login on the NAS by SSH from your computer (Windows: puTTY
, OS X Terminal app: ä ssh admin@[NAS-IP-address]) using the admin credentials. Then you can enter the commands (the [~] shows just the currecnt directory, the # is the prompt.
Does this work?
[~] # getcfg System "Force SSL"
If this is 1 - you can disable the forced https:
[~] # setcfg System "Force SSL" 0
[~] # /etc/init.d/thttpd.sh restart
Now you should be able ot login on the http channel again.