USB Modem

My modem worked fine till yesterday, Now i am facing following problem

root@deepan-desktop:~# wvdial
--> WvDial: Internet dialer version 1.60
--> Cannot get information for serial port.
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0 &C1 &D2
ATQ0 V1 E1 S0=0 &C1 &D2
OK
--> Modem initialized.
--> Sending: ATDT#777
--> Waiting for carrier.
ATDT#777
CONNECT
--> Carrier detected. Starting PPP immediately.
--> Starting pppd at Wed Jul 15 20:18:21 2009
--> Pid of pppd: 3453
--> Using interface ppp0
--> pppd: 臸 P��
--> pppd: 臸 P��
--> pppd: 臸 P��
--> pppd: 臸 P��
--> pppd: 臸 P��
--> Disconnecting at Wed Jul 15 20:18:51 2009
--> 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.
--> Auto Reconnect will be attempted in 5 seconds
--> Cannot get information for serial port.
--> Initializing modem.
--> Sending: ATZ
--> Sending: ATQ0
ATQ0
OK
--> Re-Sending: ATZ
ATZ
OK
--> Cannot get information for serial port.
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0 &C1 &D2
ATQ0 V1 E1 S0=0 &C1 &D2

Please suggest a solution