Cox Says It's Linksys' Problem. Linksys Says It's Dell's Problem. HELP PLEASE!?

I purchased a Linksys wireless-g broadband router and two pci cards over the weekend in hopes to give my two computers wireless access at the same time with no wires.  My ISP is Cox.  After I installed and set up everything, only my mother's computer could connect to the internet.  My Dell 4600 would recognize the signal but not connect.  I talked to three different people from Linksys.  They told me to uninstall and reinstall, change pci slots, manually configure the ip address, change channels, uninstall my mcaffe firewall, etc etc.  They had me do everything in the book.  Finally, the last lady I talked to had me ping ip addresses.  My computer would recieve replies from the router, but not from websites.  Due to this, she said, my computer was not resolving DNS addresses (or something like that).  She said that is caused by the manufacturer.  I am sick of talking into the phone, and was hoping soemone out there might be able to offer help.  I am sick of not having internet access on my computer.  Please help.