When using update via profile against a set of "individual" contact records, contact subtypes disappear and revert to the parent type (e.g. Student > Individual)

If you run an advanced search for "individual" contact types, and then use batch update via profile to edit one field over a selection of them, if ANY of the records edited were a contact subtype (e.g. parent or student), the subtype disappears and the records all revert to the "individual" designation.

Also tested on the 4.1 demo server.