Comment 10 for bug 68951

> So Firefox keeps "Looking up domain.whatever" until it times out. Should I file another bug
> for this?

I'm thinking you're bumping to bug # 24828 . Try disabling ipv6 in both ubuntu and firefox. Here's a howto https://help.ubuntu.com/community/WebBrowsingSlowIPv6IPv4

If that doesn't work, you may have a problematic dns server (ie it's because of your ISP). have a look at http://www.opendns.com and http://www.opendns.com/start/unix.php

PS. make sure to note the old DNS servers in case it doesn't work or something... and of course, always do a backup of it bf editing a system file.