Trouble with Purchase of LCD Backpack

I tried to buy an I2C LCD backpack on your store website. When I tried to Add to Cart, I got a validation error saying the Category is a required field. There doesn't appear to be a web control that would allow me to enter a Category, so I can't get past the validator to add the backpack to my cart.

I'm using IE 8 on XP. Could you please let me know how I can fix this?

Thanks,
Richard