Nice. Was it a normal pci slot modem? I've sometimes found that on machines that have several pci slots, like most desktop pcs do, you might get problems if you plug the modem into a wrong slot. In the beginning I foolishly thought the pci slots were more or less "identical" and it was ok to pick up any of them. Later I've learned that by plugging some pci device (usually ethernet cards in my case) into a wrong slot makes it either not function well or at all or may even cause something else stop working. Oftenmost I've figured it's just because of the IRQs get mixed, and because I have no interest in learning how to manually put them right (four minutes in BIOS was enough, after all it's just an ethernet card that I can put into another slot, and not a massive tank I can't).
Well, the bottom line is that..who the heck ever decided about IRQs or pci slot orders? Curiously enough, the problems I've faced have mostly (if not only) been with machines that have both Windows and Linux installed side-by-side, but of course I tend to think it's not because of that