Error Cannot Connect to Remote Ppp Server Verify Modem Settings


how do you solve this problem . whenever i try connecting using speedtouch modem on my mac os x ver 4 tiger i get an error saying cannot connect to remote ppp server please verify modem settings.
I have checked the dns server settings and also create new location. still no help can u please suggest how to deal with this problem, i have also reinstalled the speedtouch modem drivers. i m using dsl modem which is connected to my usb port.