could be a few things.
1) do you have a router that is assigning itself as the DNS server to your computers.
a)if yes, reboot your router or remove it and see if the problem still exists.
b)if not, what DNS server is assigned
i)paste a traceroute to the DNS server
2) are you losing packets?
3) is it to any specific site or everything you go to.
4) is it just web that laggy? can you ftp or something else that requires a DNS lookup
give me your mac address and I can also look for any signal issue that could be causing this.