unknown conflict between modem + sound c

I have a user who is using a Dataflex PC Comms 1.4k modem,, and a CMI8330 on-board sound card. The motherboard is an American Megatrends P54C. The problem I’m having is that when both of these devices are acctive in the Bios, they cancel each other out in Windows 98. Neither of the devices are visible in the system panel. I’ve tried reserving irqs, dmas and memmory addresses to no effect. Each device works perfectly on it’s own, and both are detected in the bios, which is plug-n-play 1.0A, but neither appears in the operating system. This problem has also occurred with the pci version of the sound card. Both modem annd sound card use ISA ports, even though the sound card is on board. I need both devices to work at the same time.