This just started like 4 or 5 days ago. I'm running Ubuntu 12.04 desktop, and after about 12 hours of uptime it seems the loopback device just stops working. If I do an ifconfig, it looks like it's still there, but if I ping localhost or 127.0.0.1, both fail. Also, pinging known DNS addresses (www.google.com) fail. But pinging by IP works fine.

The rest of the networking features seem unphased. I can still reach the Samba share from my Windows machine. Also, I run an Apache server that is still reachable from the outside world. Looking at the resources monitor, the CPU and memory usage appear normal when this happens.

If I restart the machine, everything is fine again. For about 12 hours, until it happens again. Any ideas on what could be causing this or how to diagnose it? Thanks.

Disclaimer: Please excuse my n00b-ishness. I'm a long-time Windows guy that just started using Ubuntu 6 months ago.