I recently upgraded from 11.10 to 12.04, and now NetworkManager isn't populating /etc/resolv.conf when connecting to wireless networks, when it had been working perfectly in 11.10. I'm not seeing any explicit errors in either the NetworkManager, UI or in syslog. How do I diagnose what's wrong?

Edit: If I try to run resolvconf, I get the error

resolvconf: Error: /etc/resolv.conf isn't a symlink, not doing anything.

What should it be, a symlink to and/or how do I get NetworkManager to populate it? This says the symlink should point to /run/resolvconf/resolv.conf, but that file does not exist on my system.