Error 619

Can anyone help resolve a 619 error ?. I have just upgraded my OS from WinXP Home (Portuguese) to WinXP Pro (english). After loading the OS I reinstalled all the drivers etc that came on the restore disks with my Dimension 4600 but can not get get online. The modem dials OK but fails to authenticate me. I checked with my ISP and everything is OK there. I searched online and a common solution seems to be to delete the dial-up connection, delete the modem and then reboot. Windows will then find the modem and install it correctly. This, however, does not work.

All help is greatfully accepted !.