Cable Modem Setup - Can't seem to get a connection

[Gene and Amy Dascher]

OK, here's the deal.  The comcast guys came out an looked things over,
installed a new line in my computer room, and left me with the
installation invoice.

I have tried everything under the sun (from a lot of different
Cable-Modem how-to's, but I still can't get this thing working.)   Here
is what is on the installation sheet:
(Some numbers have been changed to keep them relatively secret)

DNS #: CJ123456-B 
IP ADDR: 24.183.100.120
Prim DNS: 24.16.152.15
Sec DNS: 24.16.152.17

There is no Gateway address listed, and there is no subnet mask listed. 
Here is a copy of my /etc/sysconfig/network-scripts/ifcfg-eth1 file:

DEVICE=eth1
IPADDR=24.183.100.120
NETMASK=255.255.255.0
ONBOOT=yes
BOOTPROTO=dhcp
DHCP_HOSTNAME="cj123456-b"
NETWORK=24.183.100.0
BROADCAST=24.183.100.145

In my /sbin/ifup script, I have modified the pump line to read:
if /sbin/pump -i eth1 -h cj123456-b ; then

Every time I try to run ifup eth1, I see the cable light blinking slowly
on the modem, and the data light is blinking quickly, BUT it always ends
up failing.

One thing that I haven't done is use the NIC that they gave me.  I
already had a NIC that is a different brand in the PC.  I don't see how,
but could that be a problem?

The cable modem that I have is a Toshiba PCX1100.

What am I missing, and where do I go from here.  I think I am going to
write a VERY detailed How-To when this is all said and done.  There is
something to be said for learning things the hard way, but this is
rediculous.