Incorrect page re direct
We built this shopping cart over a year ago and all of a sudden this page (cupcakes.php) is re directing to its own page (cupcakes.php) when an item is added to the cart. There are other areas of this site that direct without any issues to the same cart / order display???? Not sure what is happening, we haven't been in on the account making any changes since june 11th and this problem just began today. We do see that there are some orders that have gone through, however, there have been many reports, including our own failed attempts, that there is a problem.
Any assistance would be greatly appreciated!
I've attached the page files as well as the ecart files to this post.