I have a Performa 6320CD with an internal modem (teleport silver?) and when the modem is plugged into the phone jack, it opens the telephone line and won't disconnect causing the "european siren" and "please hang up and try your call again" along with static and silence. Regular telephone works and will disconnect when the call is completed, but the modem won't disconnect. I have to unplug the modem line from the phone jack, plug it back into the wall and immediately sign on to the application using the modem to get an outside line.
This problem just began two nights ago after having the computer almost two years. I have installed no new software.