Linksys access by 2 or more Vista laptops

Hello, I have a Linksys network which worked fine with 2 or more XP enabled laptops and 1 Vista laptop accessing the network and the internet. Recently I acquired a second Vista Laptop but this new one can only connect to the network but can not access the internet. When the first vista laptop in not on the network, the newer Vista laptop is able to connect to the network and access the internet. In fact, the newer Vista laptop gets bumped off when the older vista laptop connects. How do I solve this problem. Thanks ...