Same here, and my iPad would not connect to my wifi network either. I ended up with a DFU brick.
Here is how I fixed it.
FIRST: Make sure no other device is showing in iTunes (switch wifi off on your iPhone etc.)
Then connect the iPad using a cable only.
Restore the iPad to factory settings
Now try the update nd restore.
This worked for me, and I can only assume that because my 4S was on and showing it somehow screwed up the update.
Hope it works out for you.