Same happend to me right now when adding a Brother HL-5340D. I downloaded the ppd file from http://welcome.solutions.brother.com/bsc/public_s/id/linux/en/download_prn.html#HL-5340D and provided it to system-config-printer. When I click on "Apply" I get the same "CUPS Server Error" dialog, with the text "server-error-internal-error".
$ cat /etc/issue Ubuntu 12.04.1 LTS \n \l -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/254202 Title: server-error-internal-error while adding printer To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/system-config-printer/+bug/254202/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs