Cannot ping localhost after a half day of uptime

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http://askubuntu.com – 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, 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 ()