If the suggestion in the post above doesn't work for you, you could try the entry in my File > Print > Properties... > Printer Properties > Print Command: (which reads as follows
lpr ${MOZ_PRINTER_NAME:+'-P'}${MOZ_PRINTR_NAME}
FYI: I am using cups version 1.1.23-7 x86_64 on SuSE Linux version 9.3 it works great for me.
HTH