We used to have that problem a lot on the older SOHO 3's by Sonicwall. We don't see it as much on the new TZ170's and we've got a LOT of those in service. If the LAN LED's are staying lit even when the cable is unplugged you may have bigger problems, but other than that it sounds like you've lost your firmware. (Is the wrench light staying lit?) If you go to your mysonicwall.com account, log in and go to their forum, you'll find the step by step to reload and give it a try.