Port won’t close after use

I am running Windows 98 on a PIII 650Mhz system. I have a USRobotics v90 internal modem. I have to delete the modem everytime before I shut down so that the system will reconfigure it upon startup. If I use the modem then disconnect then try to connect again I will get an error message 630. When I run diagnostics then on modem it says that it can’t open port or port is already open. I show an ACPI controller using IRQ9 which is the same interrupt the system assigns to my modem when I startup. If I try to change the interrupt to IRQ3 or 4 it says it is in use by com1 and com2. If I try to use Com1 thru 4 it tells me that they are in use.