Operating system name and version: Ubuntu 10.10 maverick
Version of smsd: 3.1.3-2. i386
Smsd installed from: apt-get install smstools
Name and model of a modem / phone: Quectel M35 ~ http://i00.i.aliimg.com/img/pb/961/314/627/627314961_218.jpg
Interface: serial / USB / some adapter... : USB
Driver : Vizzini Version 0.74

Hello smstools works fine, but after a while , I error log like :

2015-11-03 08:51:02,3, GSM1: Cannot open serial port /dev/ttyUSB0, error: No such file or directory.

after a reinstall vizzini , it fixes but after a while disconnected again.

here is the dmesg :
[ 224.233399] vizzini ttyUSB0: Vizzini USB serial port converter now disconnected from ttyUSB0

notice : usb cable not disconnected for sure.

smsd.conf :
#
# /etc/smsd.conf
#
# Description: Main configuration file for the smsd
#

devices = GSM1
outgoing = /var/spool/sms/outgoing
checked = /var/spool/sms/checked
incoming = /var/spool/sms/incoming
logfile = /var/log/smsd.log
infofile = /var/run/smstools/smsd.working
pidfile = /var/run/smstools/smsd.pid
failed = /var/spool/sms/failed
sent = /var/spool/sms/sent
stats = /var/log/smstools/smsd_stats
loglevel = DEBUG
receive_before_send = yes
autosplit = 3

[queues]
TR = /var/spool/sms/TR

[provider]
TR = 0,1,2,3,4,5,6,7,8,9

[GSM1]
pre_init = no
init = ATE0
init2 = AT+CPMS="SM","SM","SM"
device = /dev/ttyUSB0
incoming = 1
baudrate = 115200
queues = TR
cs_convert = yes
rtscts = no
send_delay = 50


any idea ?

Could be that the modem is now mounted on another /dev/ttyUSBX ? I would try ls /dev to see what devices are there.