I've tried different ports - high, low, privileged..
Due to my admin's limitations, I'll be using Calibre on a different machine.
BTW, regarding the 0.0.0.0 address - since its use is specific, I still think that the error message is misleading and should be more specific (i.e. "could not bind server with *:8080"). And thx. Toddos for his elaboration on the 0.0.0.0 address.