[metalalchemist]

Ok, posting my findings here too as it might help others(already posted a neca's facebook) :
For those asking, full story: Yesterday I used chrome; indeed when the checkout button failed, I just refreshed and luckily the second click on the checkout button went through fine(this working, was mere coincidence and luck).
Today after looking into people issues I decided to check what the deal was.
So, there is a tool under chrome named the code inspector where you can explore all ajax requests, javascript actions, etc (techie/programmer stuff, I now, but basically to check generated requests from your browser to their server)
I noticed that indeed, this time the checkout button was taking a while to do something (at least, nothing apparent), so decided to open code inspector and look under the hood.
I could see that after clicking it, the request was being sent to their server/servers?, but in some cases, the server took a while to answer back. This response time, at least for me, varied between 15 to 40 seconds.
So, my appreciations as a website developer: 1. Yeah, their site is over-saturated and unable to handle that many requests
2. Bad user interface as the experience is not very informative
3. Yes, sometimes the request can be sent and the server still not respond because it got hung on your request (this can happen to sites even without big user load)
4. As some say here: be patient with the button. What I would do in this case, given the previous already commented issues is to click once, wait a reasonable amount of time (say about 30 secs which seems to be the average) and if it does not load, refresh the page and click again once. This last step is what I used to test request duration in my experiment.
Hope it helps and hope it helps NECA - N.E.C.A develop a better site (if you want, you could hire me or I could get you a good dev contact me in exchange for access to exclusives every year XD)
Another option too, is opening a couple more of tabs in your browser all pointing to the cart and clicking once in the checkout button. One of them should load faster and you get the a bigger chance for your request not to be just dropped.