Batch membership entry sends all membership contrib receipts to the first contact

When entering membership via batch, and selecting "send receipt" for each membership entered, all of the membership receipts go to email address of the first contact on the list.

None of the other membership contacts receive a receipt.

The email receipt functionality works fine for contributions. Only for memberships does it malfunction.

The email receipts show the correct membership information - membership type, dates, etc.

However the email and Contact name (which we're including in the email via a custom contact field that has our preferred contact name for this contact) are both stuck on the first contact in the batch.

Below are some sample email messages received by the first contact in the batch just for illustration:

--------

To: John Doe <johnd@socket.net>
Subject: Membership Renewal Confirmation and Receipt

Membership Information
Member Name John Doe
Membership Type Individual
Membership Start Date September 16th, 2012
Membership End Date September 15th, 2013
Membership Fee
Amount $ 25.00
Received Date March 27th, 2012
Paid By paypal

---------------

To: John Doe <johnd@socket.net>
Subject: Membership Renewal Confirmation and Receipt

Membership Information
Contact Name John Doe
Membership Type Household/Family
Membership Start Date September 16th, 2012
Membership End Date September 15th, 2013
Membership Fee
Amount $ 40.00
Received Date April 5th, 2012
Paid By paypal

---

Etc - this contact received about 30 of these, since 30 were in the batch.

I tested this a few different ways (removing some of the extra profile fields we had added, rearranging the profile fields that we had rearranged, etc) and always all membership receipts in a batch go to the first contact list.

This is CiviCRM 4.2 under Drupal 6.