This didn´t happen with previous versions nor does it affect other programs so far, only Firefox. There are other reports of similar problems under ver 4, the difference I found is that after accepting the error message 10 - 12 times it finally does print. I can´t say if it alters the quality because I only printed common text. Following some of the suggestions given, I´ve changed the path to point to the correct driver folder, and I´ve copied lxbcprp.dll and lxbcprpr.dll to the system 32 folder. The problem remains.