The error page simply states that the item is out of stock but doesn't bother to tell me which one is out of stock. I tried a few times but the purchase couldn't go through. Sometime it shows the error page after I clicked the "check out" button as well.
I guess this is related to the issues Amazon experienced earlier this week?
Since I cannot find a good way to inform someone at Amazon about this (aside from maybe posting to HN), I'll send some screenshots to jeff@amazon and I'm sure whatever support team that still reads his email will see it.