Modem Ports already open error

I’ve installed sereval modems in a Win 98SE machine and they will connect once and then after I get no dial tone error messages, checking the modem in control panel diagnostics it gives me ports already open. If I delete the modem and reinstall andgo to diagnostics it shows OK but when I go to connect I get no dial tone, if I go back and check it again it shows the ports already open, any ideas?