Create a new user account on your system
(System Pref's/Accounts/and click on the + button)
Log into the new account and try to use itunes and see if the system reads disks. If it does then it a Plist issue and and should trash the files what Gigs recommends.
If the problem still on the...
What Ip address do u get on the mac? 10.x.x.x 169.x.x.x 192.x.x.x or 8x.x.x.x.
also what does your printer have.
Also check if u have file sharing on. use Network Manger to ping 127.0.0.1 (your ethernet port) also enter 17.254.3.183 in to web browser to see if you have a dns problem.