DSL/Home Network Problem

I just got Verizon DSL.  It uses a Westell wired/wireless modem/gateway.  I have two Dells connected to the modem by ethernet cables.  Whenever one of the computers does something on the internet, the other computer's internet service stalls for about 30 seconds .  The service is blazing fast when not "stalling".  I would think the DSL connection would share bandwidth, not just direct it to one or the other computer.  The two computers are "home networked" together, but sharing is turned off on both.  (I created a setup disk using the primary computer and used it to set up the secondary computer) 

 

Here is how I have them set up:

 

Primary computer (with Verizon software)

connected to ethernet port 1 of the modem

2 connections shown under "Network Connections",  one lan and one Verizon DSL

ZonesAlarm firewall active

 

Secondary computer

connected to ethernet port 2 of the modem

1 lan connection shown under "Network Connections"

Windows XP firewall active

 

Modem hardware firewall set to lowest level protection

Wireless performance disabled

 

Any idea what I'm doing wrong?  Is the secondary computer trying to use the internet connection as a slave to the primary computer?  (I don't think so, since it works fine when the primary computer is turned off)  Do I even need to network the computers together? 

 

Please help

 

campcod