Firewire Troubles

I am able to successfully send jobs to a Mimaki JV3-160SP via a 6' firewire cable, however when I change the firewire cable to a 15' cable, I receive Error 23 Host I/F on the printer LCD. I've been receiving this error for a while, and to try to resolve it, have replaced the motherboard and firewire connector on the Mimaki, replaced the 15' firewire cable, and replaced the PC firewire card (made sure it has a Texas Instruments chipset). I've run out of things to replace other than the PC's motherboard. Has anyone else experienced this issue or does anyone have any suggestions to reslove the issue? As usual, Flexi doesn't offer much in the way of support for this.

Thanks.

PC is 160GB 7200 RPM SATA, 4GB RAM DDR2, Windows XP Pro SP3, SIIG Firewire [FONT='Times New Roman','serif']3-port PCI 1394, Intel Core 2 Duo E6600 2.4GHz, Intel ATX Motherboard, Radeon X1550 512MB PCI-E Video Card[/FONT]