Due to a hardware failure, bazaar.launchpad.net is offline at the moment. We expect it will be back up and working correctly in about an hour or two from now. (That is, by about 17:00 UTC on the 21st of January.)
This affects all bzr-branch-related services: ssh and http access to branches, and also browsing of branches.
If you saw an “incorrect data check” error or similar from bzr while branching from Launchpad, this is probably the reason why, and the problem should be fixed soon.
Update: Code hosting is now back online. We’re sorry for the inconvenience.