Modem Issue

Installed new Lucent V.92 modem. Dial up appeared to work properly. Upon next attempt to dial up, error message appeared. It stated that modem was not physically installed or the line was not connected. Upon checking modem diagnostics, communications could not be made with modem, and “port already open” was replied. Upon removing device via device manager and refreshing. Windows found modem, installed software, then dial up worked properly. Then upon disconnecting and attempting to reconnect some time after, same problem again, with the same results.