A small gotcha witha too smart printer.
I have a PostScript capable printer (Lexmark C510) connected to one computer and I ofter print to there from my notebook trough CUPS. I noted that sometimes the printer would blink "busy" lamp and then go back to "ready" without printing anything. Usually I just printed to a PS file, converted it to PDF with ps2pdf and then it worked. (I had no time to investigate then)
Now, I found, what the problem was - some apps on the notebook were generating Letter size Postscript and the printer only had A4 paper, so it simply ignored the data after parsing it. Doh!