Well I seem to have narrowed the problem down. I've found 3 specific products that cause the cart tables to break.
Dynamic - "Photosynthesis" - CD
http://www.axiscc.com/~fatbelly/store/product.php?productid=16148&cat=256&page=1
Blue Star Music Camp - Student Concert Videos
http://www.axiscc.com/~fatbelly/store/product.php?productid=16184&cat=262&page=1
Shantytown - Trying To Find The Door (mp3 download)
http://www.axiscc.com/~fatbelly/store/product.php?productid=16148&cat=256&page=1
I haven't tested all of the products but from what I can tell the rest seem to be working fine. And I tested at least one of each set of clones.
Now for the big question. What's wrong with these specific products that are causing this. I've gone in and checked everything and I can't find anything specific as to what would cause a problem.
Does anyone have any ideas what could cause a specific product to cause the cart tables to break?
As always, thanks for your assistance.
JB