Every few minutes, when I request a web page, I get a DNS lookup failure. Usually, if I just immediately refresh, the web page will come up. However, recently the DNS failures have been persisting for long periods of time, even across restarts (though eventually, it always starts working again, at least for a while). It happens in Chrome, Firefox, Thunderbird, and Update Manager. When this happens, if I ping a host name like www.google.com, I get an unknown host message, but if I ping an IP address, it works fine.
I'm also running Windows 7 in a VMWare virtual machine on the Ubuntu host, and if I switch to the VM, I have no problems, even when the host Ubuntu is having DNS failures.
Note, I'm using a wired ethernet connection.
Thanks for any help.