I have had this happen a couple of times. I cannot access my ISY-99 by entering its IP adress, through network (it does not appear in network), or through the web site http://www.universal-devices.com/supp.htm (My ISY).
I unplugged the ISY and now it works fine.
What's the deal? Is that normal. I am going out-of-town, and do not want it to lock up while I am gone.