I know it's been a while since you posted, but I can help. I just bought a officjet pro 7680. and was having some trouble with getting it to work on the ethernet.
first I have trouble with the software not letting windows shut down. the problem is with "digital imaging monitor"
so I had to disable it from starting with windows using "msconfig" If you want to know more about that too, I can help.
but on to the printer.
what have you tried so far?
I ended up setting my printer on manual network settings to keep it from changing the ip address.
second, I used the printer properties to change the Ip address in the computer.. after that, it worked finally.
I followed this guys steps and it worked.