Richard - I am terribly sorry you experienced this. Apparently according to the provider of the store software, there has been some sort of intermittent glitch. At 3:30 this morning when I couldn't sleep I found your message and checked it. I too had the same issue. Ten minutes later everything was just fine. I contacted the provider and they are looking into the long term solution. If you go to the store and try again - and it fails, would you be willing to send me an email with the list of the item/s you wanted and I will send you an invoice via PayPal or Google Checkout, whichever you prefer.
Anna - There was apparently a setting I failed to chekc when I created the coupon. That has been resolved and I am terribly sorry you experienced this. The setting was not exactly obvious to me and had a default soend limit fo 25 dollars for some reason.
There as a third issue I experienced with my store on Sunday. Because of that and now this, we have made the decision to ditch out current store and replace it with something else rather quickly.
Again, I am sorry for the issue you both experienced and look forward to getting it right next time.