Price changes on checkout when using istraxx_ups extension

[mommomami]

We have recently upgraded a client's site to Joomla 2.5.6, Virtuemart 2.0.10.  The site is http://thestainstore.net/ 

The problem we are having appeared when we added the istraxx_ups  extension.

The problem is when we go to checkout, the product prices change.  This happens at the point where a customer provides their shipping information.  For example, the product HCorp Chemical Stain, found under Acid Stains (http://thestainstore.net/products/acid-stain/hcorp-chemical-stain-detail.html) goes from $58.00 to $58.05 when shipping info is added (it does not matter if the person logs in first or not--they can be checking out as a guest or as a registered user and it still happens.) 

Any idea what is going on? 

This is a live site, so would really love a quick solution.

Thanks!

[mommomami]

Additional info:
This problem does not appear when using Chrome.  Having problems with Firefox (15.0.1) and Safari (5.1.7) on a Mac.  Have not tested in Explorer yet.