[ubuntu] Empty resolv.conf, short names not working

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http://ubuntuforums.org – Installed 12.04 recently on Thinkpad T420. Things were working fine but don't know what might have screwed up the network manager. Many a times, after connecting to wired LAN on office network, the resolv.conf comes up empty and I am unable to connect to the office servers with shortnames If I change the resolv.conf manually, then switching from wired lan to my usb dongle at home doesn't change resolv.conf and I again run into issues connecting since it is still looking for DNS pointing to office IPs Not sure how I reached this state :) Any ideaz how to fix this ? (Hardware)