Прикол в том, что модем звонит, связывается с провайдером, некоторое время простаивает и кладет трубку, вот что пишется в журнале Gnome ppp:
--> Ignoring malformed input line: ";Do NOT edit this file by hand!"
--> WvDial: Internet dialer version 1.56
--> Cannot set information for serial port.
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
OK
--> Modem initialized.
--> Sending: ATM1L3DP5640000
--> Waiting for carrier.
ATM1L3DP5640000
CONNECT 115200
--> Carrier detected. Waiting for prompt.
--> Don't know what to do! Starting pppd and hoping for the best.
--> Starting pppd at Sun Sep 9 14:43:29 2007
--> Warning: Could not modify /etc/ppp/chap-secrets: Permission denied
--> --> CHAP (Challenge Handshake) may be flaky.
--> Pid of pppd: 8928
--> Using interface ppp0
--> Disconnecting at Sun Sep 9 14:44:06 2007
--> The PPP daemon has died: A modem hung up the phone (exit code = 16)
--> man pppd explains pppd error codes in more detail.
--> Try again and look into /var/log/messages and the wvdial and pppd man pages for more information.
Куда смотреть, что читать, ткните в ман