git-checkout sometimes silently fails

I've had this happen before and I don't know what to do to make it stop. Usually sufficient fiddling will prevent it from happening.

y:/usr/src/git26> cat .git/branches/linux-next git+ssh://master.kernel.org/pub/scm/linux/kernel/git/sfr/linux-next.git

y:/usr/src/git26> git-checkout master
Switched to branch "master"
y:/usr/src/git26> cat kernel/*.c|sum
34439  2057
y:/usr/src/git26> git-checkout linux-next
Switched to branch "linux-next"
y:/usr/src/git26> cat kernel/*.c|sum     
34439  2057
y:/usr/src/git26> git-checkout origin 
Note: moving to "origin" which isn't a local branch
If you want to create a new branch from this checkout, you may do so
(now or later) by using -b with the checkout command again. Example:
  git checkout -b <new_branch_name>
HEAD is now at 5717922... Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb
y:/usr/src/git26> cat kernel/*.c|sum          
34439  2057

y:/usr/src/git26> git --version git version 1.5.5.rc1

help?