My device was working perfectly until  I had a power failure. Now, upon turning on, the WD light will flash for aprox. 20 minutes for which I don’t have access to the hard drive via network, after that everything is ok.

I tried updating to the latest firmware and factory reset. I am wondering if I should reform the Hard disk using the setup utility and/or about any other ideas.

You stated that you don’t have access to the internal drive of the WD TV, through the network, but, are you able to access the drive contents, using the remote? Can you play your movies before that 20 minutes mark?