I'm on 12.04, I upgraded a month ago from Windows 7 on my Sony VAIO.
Everything is great except after the upgrade, I encountered Internet connectivity issues.
When browsing the web or loading videos, my Internet will stop working in the middle and come back after a period of 30 seconds to 2 minutes or sometimes it just won't and I'll have to disconnect and re-connect to the network. I've noticed the issue when sending e-mails as well, they just won't send at all.
It says sending request and the circle keeps spinning slowly until I get to a page where it says the page wouldn't load and gives me the reason DNS error. I tried setting OpenDNS as my DNS provider but that didn't help.
edit: Error message is actually "webpage not found because the DNS lookup failed"
I decided to take out my wireless adapter and use a new USB D-Link DWA-160 revision B2. I'm still getting the same issues with internet connectivity dropping during the loading of connections.
The same connectivity issues plague me even while connected through the Ethernet port.
I have no wireless adapter in my computer and an Ethernet port as well but I have the same connectivity issues and dropping of the connection randomly so I can't figure out the cause.