apt-get update 'extras.ubuntu.com:http' fail

ubuntu 12.04 beta1
'apt-get update' fails on one source with:
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Err http://extras.ubuntu.com precise Release.gpg
  Something wicked happened resolving 'extras.ubuntu.com:http' (-5 - No address associated with hostname)
...
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/precise/Release.gpg Something wicked happened resolving 'extras.ubuntu.com:http' (-5 - No address associated with hostname)

E: Some index files failed to download. They have been ignored, or old ones used instead.
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I am guessing that it is treating the ":http" as part of the hostname. Sounds like a typo to me.