Ever had this error when trying to print from Firefox? It's annoying as it pops this message up before even a printer selection or any printer dialog boxes appear, so you can't do much trouble shooting. The solution is below, taken from: http://forums.xandros.com/viewtopic.php?t=27050
about:config Next in the filter bar type print.printer_PostScript This filters out all but the entries that start with this string. Find the following the following entrie print.printer_PostScript/default.print_paper_height double click it and change the value to 279.40 Next find print.printer_PostScript/default.print_paper_name And change this entry to Letter Finally find print.printer_PostScript/default.print_paper_width and change it to read 215.90 Close FireFox and re-open, you should now be able to print.
I didn't need to close Firefox, worked straight away. I found the letter size was "na_letter" for me, so that's the one that did it for me, oh also margins were all 25 apart from bottom margin which was 56, so I made it 25 as well. One of those fixed it for me.