Why did I lose the ability to print to a networked printer?
I had the same problem and this is what I did to fix it:


Go to http://localhost:631/

If you get the "Web Interface is Disabled" message, run cupsctl WebInterface=yes in Terminal.
Choose the Administration tab.


Click Add Printer.



If you are required to login, use a local Administrator account.
Select the printer (in my case it was automatically found).