<blah> hi, i have to say I hate Z6 wholeheartly. The 2nd time i want to use Z6 as a bluetooth gprs modem for my laptop turned to be a total failure,:it always get refused when try to connect rfcomm0 devices.
But someone says that failure is mother of success, though maybe a step mother
</blah>
here is the trick how to wvdial your Z6 through usb cable:
1. modify wvdial.conf, add a clause "Stupid Mode =1", eg:
[Dialer hellomoto]
Init1 = AT
Init2 = AT+CPIN?
Init3 = ATE0
Init4 = AT+CGDCONT=1,"IP","cmnet"
Init5 = AT+CGQREQ=1,0,0,0,0,0
Init6 = AT+CGQMIN=1,0,0,0,0,0
Phone = *99***1#
Modem = /dev/ttyACM0
Password = ''
Modem Type = USB Modem
Baud = 460800
ISDN = 0
Username = ''
; Phone = <Target Phone Number>
; Password = <Your Password>
; Username = <Your Login Name>
Stupid Mode = 1

YOU CAN READ MANUAL OF wvdail.conf TO FIND MORE REFERENCE.

2. "wvdial hellomoto", viva! you now can surf internet with EDGE/gprs network. ( I think this trick works with some mobile operater (ISP) customized Z6 models, mine is this kind of r*ped shit)

I wish this could be helpful at least with ppl who'd like to use bluetooth headset and use the phone as modem at same time -- since my Z6 dont permit more than 1 bluetooth connections.