Very, very slow sending to printer

I am building PostScript print jobs that when printed to a Konica Minolta 1050 will produce folded, stapled and trimmed 8.5 x 11 inch booklets. The imposition is done in an application that builds it from multiple Òprint to fileÓ jobs done by other people. Since I have no control over the input, and the multiple jobs are through different drivers operating systems the application spends considerable effort converting them into clean PostScript, then imposing the PS and wrapping it in the commands to finish it properly, and the final imposed job is quite large. Sending the job to the printer produced the correct output, but took forever. I observed from the system monitor that I was averaging about 60 kilobits per second to the printer. However, when sending the same job to a printer queue (or a shared folder) on a Windows computer I got around 10 megabytes per second. If I sent from the Windows computer to the printer I got about the same 10 megabytes per second. Currently the fastest method by far is to print using the Windows machine as a print server. I did test for bad connectivity at the printer end by moving the patch cable going to the printer to a laptop running an LPR queue: I got 10 megabytes-sec from both the Windows and the Linux boxes. The problem is Linux-CUPs talking to the printer. Linux to Windows or Windows to printer is fine.

Though I am a Linux newbie, this does not seem right. Where should I be looking for my problem? The printer manufacturer is no help, at least, not in the short term.

Running Fedora Core 5, on a Sun Fire X2100 (2GHz Opteron) with gigabit Ethernet. (The printer has only 10-100.) The Windows tested was XP Pro on an identical X2100 (and also the laptop, a Pentium 4).