In Edgy this is caused by incorrectly setting the dial-out command to "ATDTW" or "ATDPW" instead of "ATDT" or "ATDP" in /etc/chatscripts/ppp0.
In Edgy this is caused by incorrectly setting the dial-out command to "ATDTW" or "ATDPW" instead of "ATDT" or "ATDP" in /etc/chatscript s/ppp0.