This normally refers to a PCI modem that has not been correctly installed or where the drivers for it are in question somehow.
Have you made any recent system changes at all, either hardware or software that you can pin this fault down to ?
Is your modem working correctly ?
Try checking out the device manager and look for any faults listed to do with your modem. Any errors will have a code of some kind in the device properties which should help you identify the nature of the problem.