Products not removed from inventory?

[sleepigrl]

I'm not sure if I've got something set up incorrectly or how things are going wrong, but none of the products purchased in my shop are being removed from inventory (nor do they get added to Booked/Ordered).  That includes items that are ordered (in Pending status) or marked as Confirmed or Shipped.

Any ideas where this could be going wrong?

Site info:  VM 2.0.12f,  Joomla 2.5.7,  php 5.3.13

I have another VM site running version 2.0.8e on the same server and products there ARE subtracted from inventory.  The frustrating thing is that on the older site, I don't care about inventory, but on the newer one I need it to function.