Xp/vista wireless with static IP

Hello, I've got a Dell desktop running Xp Home SP2 and a Linksys router acting as an access point for my home network and 2 laptops: an older eMachines w/xP Home and a newer Acer w/ Vista. Because we can't get broadband where we are, we have internet access using a cellphone as a USB modem for our desktop. This works really well for the xp machines by setting them up with static IP addresses and using the desktop as host. I thought this would work for the vista machine as well but so far it hasn't. I can't get the shared internet connection to work on the vista machine. I can see everything on the network, access files and print from the vista machine and the other machines can see and access it as well, I just can't get to the internet using the shared connection. The vista machine even registers when the host is online but something prevents web pages from loading in any browser I've tried. This only happens on my home network, any place using DHCP seems to work fine. Is it something with xp, vista or both? I'm fairly new at this so any help will go a long way. Thanks in advance