Cannot connect to internet when modem connected to router

Hello

I have just bought a D-link DI-804V router with 4 port switch and
Westell 6100 broadband modem (dual connection modem - usb and
ethernet).

I can happily get on the internet by connecting the modem directly to
the computer using either the ethernet or usb connection and setting
up the modem to connect to my internet account while acting as a DHCP
server.

However, when I try to set up the modem to act as a bridge modem to
the router and let the router connect to my internet account and act
as the DHCP server, I cannot get on the internet.

The router works fine and the link light appears on both the modem and
router so they must be talking, but the modem activity light on the
router never blinks when I try browsing the web. Also on the device
status section on the router, the diagram shows a broken link between
the router and the modem.

I have disabled DHCP on the modem by going to "DHCP Configuration" and
setting it to "Off", and simply changed the top "VC Configuration" to
use "Bridge" protocol instead of PPPoA. The router uses PPPoE to
connect, but I have tried this on the modem directly aswell and it
works.

On all the help web sites I have been to this is all that needs to be
done, so I am a bit stuck.

One thing I have noticed is that on the modem "Private LAN
Configuration" section, the "Private LAN Enable" is checked and cannot
be unchecked as it complains it needs to have either private or public
lan enabled. This leaves a setting for the "Modem IP Address" as
192.168.1.1. I cannot however ping 192.168.1.1 from the computer when
the modem is directly connected, so I assume this must be disabled if
DHCP is disabled? The DHCP settings for the router are set to pool
from 192.168.0.100 to 192.168.0.254, and the router IP is 192.168.0.1.
I dont know much about IP addresses/subnet masks etc so I dont know if
any of this will cause a problem.

Any help would be great.

Paul