Adding a coupon code triggers a purchase

Hi,
if I click on ADD (coupon code) in the checkout process and have checked the terms of use, the checkout purchase is finished immediately. And: the coupon code isn't considered!

My product costs 299 Euro.
My coupon configuration is this one:



EDIT: OMG, in the third try I couldn't reproduce this problem. Maybe I am just too tired at the moment and there isn't a bug. Sorry in this case!

That might be possible if you have a javascript error on the page. That would result in the form being submitted without taking into account the coupon, like if you click on next. Not sure if that gives an insight on your problem ?