Peter, is this the workflow that you used?

  1) remove the email address that you want to use as your
     primary address from alternate addresses. Commit the change
  2) change the primary email address to the one you removed in 1
     and commit the change.

Bascially create two separate transactions rather than trying to do it
a single transaction.

Do you get a failure at 1, or 2 or does it work?

-- rouilj