Browsers on Internet do not connect

Hello, ever sense my computer had a crash about a month ago my Internet browsers such as firefox and Internet explorer are not able to connect to the Internet through http adresses, but if I type in the network gateway or the website such as 72.14.205.103 (google) it goes to the wesite page, but from there if I try to search something the page "address not found" pops up. This goes for all websites, and I see this message every time I start a browser. Some programs such as limewire and ventrilo are still able to connect and are not affected by this. I have already went through the three hour phone call with at&t (dsl provider) and they confirmed that it is not the Internet itself. When I view the network connection on my pc it still says that I am connected and recieving connection (alot less than usual though.) I share a LAN connection with 4 other computers and they are not affected. When I called a tech support line, they couldn't find the problem, but suggested a "DSN" problem or something like that. Does anyone know how to get to the dsn page or have a suggestion about how to fix this problem?