UPS-XML module not getting right number of boxes from Zen Cart

Hi,

Background: a site that sells products that ship in multiple boxes. The parts of a single product are too big for re-packing into one box.

We installed the Canada Post module, and set all the parts as separate products, adding the dimensions and weight of each into the admin improvements that this module gives us. With the assistance of thatsoftwareguy.com's add-ons Combination Discounts and Buy The Set, we can now add a group of products to the cart with one click.

The Canada Post module gets it - that is, when we add a product with 3 parts to the cart, it quotes on shipping 3 boxes.

But the UPS-XML module reports on the price to ship one box.

Here's a sample order result from Step 1 of checkout...

Canada Post (3 box(es) to be shipped)
Xpresspost, 2008-11-14 $207.45
Expedited, 2008-11-20 $72.99
Regular, 2008-11-24 $72.99

United Parcel Service (1 pkg x 20.35 kgs total) $75.51
UPS Standard, ETA: November 17, 2008

The three boxes in this case weigh 5.6, 8.75 and 3.0 KGs. (The astute observer will notice that the UPS weight is out by the weight of the third box, but that is a coincidence -- the tare weight happens to be 3 KG, which may be an error in our setup but is not part of the problem.)

The developer of the UPS-XML mod is stumped. He's not a full time programmer, and my PHP skills are limited to copy and paste. Debugging is beyond me.

Can anyone help with figuring out what is wrong?

(If you set up an account on the site to work on the problem, please identify it in some obvious way so we can easily delete it later. There's no need to complete an order to see the problem; you just need to get more than one product into the cart, then go to Checkout Step 1.)

TIA

Rob