I have this modem  ZTE k3765-z . And i cannot to connect(i configured by this http://wiki.openwrt.org/doc/recipes/3gdongle  )
The usb mode switching was succesful (thanks to http://www.draisberghof.de/usb_modeswit … ff9fc7605b )

ifup wan gives me this error
timeout checking for PIN.wan(3g): Failed to set the PIN code.

(i checked pin code  under windows - its works)
Also i can connect with this modem on debain 6 by network manager(but how to find the AT command which it sends)

configs:

config interface wan
        option ifname ppp0
        option pincode ****
        option device /dev/ttyUSB1
        option apn A
        option service umts
        option proto 3g
        option username a
        option username a

[I remove the pincode and apn ,usernames due the some reasons]

cat /etc/chatscripts/3g.chat
ABORT   BUSY
ABORT   'NO CARRIER'
ABORT   ERROR
REPORT  CONNECT
TIMEOUT 10
""      "AT&F"
OK      "ATE1"
OK      'AT+CGDCONT=1,"IP","$USE_APN"'
SAY     "Calling UMTS/GPRS"
TIMEOUT 30
OK      "ATD*99#"
CONNECT ' '

[P.S i also tried with different  number OK      "ATD*99***1#"  ]

Some additional details.
I run under virtualbox(usb device of course is ocuppied by virtualbox handle) - the virtualbox is latest.
Openwrt
DISTRIB_DESCRIPTION="OpenWrt Backfire 10.03.1-rc4"
DISTRIB_TARGET="x86/generic"
DISTRIB_REVISION="r24045"