When I tried to print something I would get a "Preparing Preview" hang. Other support answers, suggested 1. deleting the default printer 2. delete some custom settings in about:config Both solutions did not work for me. In my case it turned out the firewall was the issue: During the Preparing Preview, firefox tries to connect to port 80 then port 631. In my case, the firewall was dropping everything except RELATED/ESTABLISHED. Opening port 631 for the printer did not help either, because firefox was trying port 80 first. Since all requests were silently dropped (default IPtable policy), firefox waited forever for an answer. Now with the following rules, it worked. [0:0] -A INPUT -p tcp -m tcp --dport 631 -m state --state NEW -j ACCEPT [0:0] -A INPUT -p tcp -j REJECT --reject-with tcp-reset These rules needs to be on IPV4 and IPV6 firewalls.