Having trouble connecting Vista to my home's network

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I just bought a router called Linksys WRT54G firmware 7.0. My Vista
disconnects the whole modem- router connection whenever I try
to connect it to the network. The weird thing is it only happens when
other devices are connected to the network prior to Vista's
connection. And it is always the Vista who "destroys" the whole
network. However, if I connect the Vista first and then connect other
devices, everything will be fine. What is the cause of that?

 

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DHCP is enabled.By destroy I mean the connection between the modem and the
router is forced to disconnect. However, If I unplug the the Ethernet cable
or disable the wireless of my Vista laptop, the connection will resume and
everything is back to normal. I strongly suspect this is due to Vista since I
have tried various devices and none of them causes this problem. And I dun
think I can check the IPs since the connection is lost whenever I connect my
Vista....