Removing directory from HEAD

I am trying to rm the po directory from event HEAD to replace it with a translations directory:

cvs rm -f po
cvs remove: Removing po
cvs remove: scheduling `po/ca.po' for removal
....

cvs ci -m "removing po directory" po
cvs commit: Examining po
** ERROR: Your commit is using a 'Sticky tag' which corresponds to
** a branch which is not valid in this CVS repository. If this
** commit were to proceed, you would create an invalid branch:
** HEAD
**
** See http://drupal.org/node/198469 for more information.
cvs commit: Pre-commit check failed
cvs [commit aborted]: correct above errors first!

Am I doing something wrong or is our pre-submit check overzealous?

The checkout doesn't have a CVS/Tag file at all...