Solved it - the config file didn't have anything for the E122. In case anyone wants it, here's the configuration entry I created for it:
[usb_modeswitch,conf]
########################################################
# Huawei E122 (HSPA+ modem)
#
DefaultVendor= 0x12d1
DefaultProduct= 0x1446
TargetVendor= 0x12d1
TargetProduct= 0x1001
MessageContent="55534243123456780000000000000011060000000000000000000000000000"
CheckSuccess=5
And to get everything happening, I invoke this script file as root:
[/root/3g_connect]
#! /bin/sh
usb_modeswitch
wait 3
wvdial
cp /etc/ppp/resolv.conf /etc/resolv.conf
Where wvdial.conf has the following:
[wvdial,conf]
[Dialer Defaults]
Stupid Mode = 1
init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2
Init3 = AT+CGDCONT=1,"IP","3netaccess"
Modem Type = Analog Modem
Phone = *99#
ISDN = 0
Dial Command = ATD
Auto Reconnect = on
Carrier Check = yes
Username = three
Password = three
Modem = /dev/ttyUSB0
Baud = 460800