This needs to be followed up on urgently. This is still an issue for the newest version of TomatoCart - v 1.1.5.
OS: Windows 7 x64
Browser: IE 9, IE 8, IE 7 (tested in each one)
Same behavior as already described. And if you use the "Buy Now" button, it gets added to the cart but then if you click on another "Buy Now" button for another item then the other item in the cart shows a crossout line through it and then the newly clicked item gets added. (at least it shows in the little Shopping Cart box in the upper-right hand corner, but it's still not actually in the shopping cart if you click on the "Cart" button to see the shopping cart contents)
The following images are in order of execution. Hopefully they allow you to get an idea for what is happening and why it's such a huge issue.
I know you guys have a lot of priorities but please move this one up on the list as it renders the entire shopping cart unusable.